Scientific plant classification

Three inter-related articles address the problem of establishing a consensual systematization of our knowledge about the relationship between plants and people. The investigation begins with a study of classification as a means of establishing the grounding principles for such a study. It then moves on to discuss plant classification in general, not just the formal scientific study of plant taxonomy. The final article, plant-people taxonomy,  tackles directly the problem of establishing a new academic discipline, the study of plants and people. The article plants and people provides an introductory context.

Introduction – Scientific Plant Classification

The article on classification discussed the process we go through when ordering our thoughts. It is this process that converts the maelstrom of sensory input pouring into our brains into a meaningful experience.

The mental process of classification itself can be a private, unconscious, and individual matter – an automatic mental computation as a process of discrimination – as when we orientate ourselves to the objects around us when driving. This can be compared to the mindless aspect of biological agency.

But classification can also be part of a public collaborative and progressive system of representation that contributes to collective learning – as when we construct the various classification systems used by science.

The article on classification examined the notion of classification in its broadest sense. It described the way our minds think in mentalese^[5] and manipulate ideas using a mental process with at least four key computational ingredients: segregation, focus, grouping, and prioritization.

(a) segregation – divides the world of experience into meaningful operational units of thought called categories (concepts, or units of mental experience)

(b) focus – restricts our attention to a manageable number of categories (creating a foreground and background)

(c) grouping – arranges categories into groups using selection criteria that are meaningful in relation to desired objectives – the structure of groupings in particular cases is called the classification system

(d) ranking (prioritization) – arranges groups into a ranked order – which facilitates action or decision-making

Principle – given a particular purpose – classification then entails at least four key context-sensitive computational ingredients: segregation (the determination of appropriate operational units or categories), focus (refining the number of categories used), grouping (arranging categories into groups based on selection criteria determined by the purpose of the classification), and prioritization (the prioritized ranking of groups).

The study of plants

For convenience we can refer to the totality of human plant knowledge as ‘plant collective learning‘ with that portion of knowledge considered of general communal significance taught as plant science in educational establishments. Some of this knowledge we value more than others. It is of general interest that (effectively) all plants photosynthesize but of little interest that I have broccoli growing in my vegetable patch.

So, in what ways is scientific knowledge special? For the time-being a simple list of scientific factors will be considered:

Given the discussion so far, how are we to understand the study of plants?

We know that we can classify plants in an infinite number of ways, for example, in relation to all their properties – colour, shape, taste, where they grow etc.

Since each classification has its own purpose, how can we prioritize one classification over another? Surely, the most we can hope for is the best possible classification given the particular purpose under consideration?

And yet in academia it is scientific classifications that are popular. Why is that?

Scientific classifications

For ease of communication, the categories we use must be as clear, distinct, and defined, if possible, by necessary and sufficient conditions (classical) rather than family resemblance (fuzzy). Since the study (our focus) is plants, then we need not only a clear understanding of what we mean by ‘plant’ but we also need a shared understanding of the different kinds of plants. This cannot be an arbitrary matter; it must be based on evidence that can be agreed by a community of experts.

This gives us a practical starting point for our human understanding of plants. We wish to know what applies to all plants at all places and all times. Then we can determine what applies at particular places, particular times, and particular instances.

The origin of botany, as the study of plants, is generally traced back to Theophrastus and the Lyceum of ancient Athens. As a distinctive study attention was drawn to the study of plants themselves rather than their uses. But confining the study of plants to plants alone is extremely difficult, not only because plants do not exist in isolation but in interaction with their surroundings, but also because human interests soon appear. The ‘purist’ pursuit of the description, classification and general documentation of plant kinds and structures that dominated Western plant study in the 17th and 18th centuries gave way to functional physiology and its application in the commercially-based plant activities of agriculture, horticulture etc. This was treated as applied science – but it was both science- and plant-based nevertheless.

This begs at least three key questions:

(a) What is it that distinguishes academic plant studies from other plant studies and, more specifically, what is it that makes a study science, and how would you go about creating a new science?

(b) What has been the historical development of the content of academic plant studies?

(c) What should be the focus of plant study today?

These are challenging and potentially rewarding ideas that are well worth exploring.

Plant classification

The key category under investigation on this web site is the category ‘plants’.

When we think of plant classification, we tend to think scientifically – of the basic plant unit as the species and the grouping of plant species into genera, families and so on. But, in principle, the scope of plant classification is much wider – it includes all possible plant relationships – not just those that exist between plants and other plants.

To reduce the complexity of such an approach we can, however, consider the three key plant relationships that are implied in the title of this web site.

(a) plants and people (cultural history of plants)

(b) plants and other plants

(c) plants and their wider environment.

These three domains of plant study form the foundations of a plant science that could unify the disparate and seemingly unrelated subjects that exist today.

Of these three relationships, it is only that between plants and plants that has become the subject of serious scientific study, becoming the discipline first known as botany but evolving into plant science. Certainly, aspects of the other two relations are under scientific investigation but not in the comprehensive way that plants have been treated.

We are inclined to think of plant classification in a narrow sense, as the biological classification of plant kinds but, were the scientific study of plants to be reinvented today, the three relationships listed above could provide a broad foundation on which to build. With this in mind, it will be useful to quickly run through the circumstantial historical course of development of plant science.

Historical development of plant science

Although studies closely resembling modern plant science were carried out in the Lyceum of ancient Greece, modern plant science emerged as an academic discipline in the mid- 15th century when chairs of botany (professor simplicium) were established in the medical faculties of the universities of early modern Renaissance northern Italy. These professors of botany were placed in charge of medicinal physic gardens so they had a new role as plantsmen, although the focus of plant interest was still the medicinal properties of plants. They were plantsmen-physicians – apothecaries in the making.

Nevertheless, this change marked the birth of botany as an academic discipline, though still strongly associated with medicine. The physic gardens they managed were what might be called a hortus medicus with plant description an adjunct to good medical practice. The objectives of these gardens, generally accepted as being the first botanic gardens of the modern era, were extremely limited in their content, objectives, and audience when compared to the botanic gardens of today. The botany they supported (description of plant kinds) was equally unambitious by today’s standards. But the picture would widen from here.

Academic plant studies were confined to the relationship between plants and plants. It would take until the time of Linnaeus for there to be a consensus on a European methodology for plant inventory that took account of nomenclature, terminology, description, and classification.

Narrow academic interest in the medicinal properties of plants broadened into the detailed discrimination of plant kinds and their inventory. This program of descriptive botany occupied early European botanists for a period of about 200 years and was given added momentum by the flood of introduced plants during the Ages of Discovery and Enlightenment in a period of European colonial expansion.

Considering the potentially wide range of plant study (the relationships outlined above) it is remarkable that plant description would be the major occupation of academic botanists into the 19th century, leaving a legacy of botanists persisting with the study of plant taxonomy, considered a foundation for any further plant study.

In retrospect, a more likely academic path for the study of plants might have flowed from the human dependency on plants for food. This probably did not occur because it was the historical academic class of educated priests and scribes who maintained community records. These men were not engaged in the toil of food production. Educated ancient Greeks, for example, were notorious for their avoidance of manual labour, which was considered distasteful. In the Greeks there was also the austere approach to plant study that aimed to remove human interest. Aristotle had chastised the endless pursuit of plant utility as tiresome, urging a study of plants for their own sake. Though the ideal of scientific detachment was admirable, focusing attention firmly on the detail of plants themselves, it was an approach that closed off a large potential territory of scientific research along with an assumption that studies entailing utility were somehow unscientific. Medicine (the source of botany) has always been a highly respected science, but is firmly grounded in human interest.

Plant study did, eventually, expand its academic horizons beyond description and inventory. Practical knowledge of food production techniques and theories date back 10,000 years to the Neolithic Revolution but, though the study of agriculture reached a temporary high during the Roman era, it did not achieve the distinction of being considered a science. It is staggering that agricultural science, as an academic discipline, is a 19th century development investigating the properties of soil and exploiting the plant knowledge gained from the wave of discoveries emanating from studies in plant physiology.

In summary, from the birth of academic botany in the mid-16th century until around the time of Linnaeus in the mid-18th century the study of plants was not only confined to the relationship between plants themselves, it was further confined to descriptive botany alone – the discrimination of plant kinds. Only in the 18th century did the study of ‘plants in relation to plants’ widen to include greater consideration of anatomy, physiology (crude experiments on photosynthesis and respiration), geography, more obscure plant groups like lichens, bryophytes, algae.

By the 19th century the wide application of new technology and the ever-present human dependency on plants was reaching into academia through horticultural colleges, forestry departments, and agricultural science.

In summary: the 200 year period of plant description and inventory that lasted from around 1550 to 1750 was concerned with the relations between plants expressed in terms of static morphology – a study of plant kinds and their structures and here reduced to the term ‘botany’. This was followed through the 19th century with a gathering proliferation of academic subjects and the continuing study of plant properties; but now the emphasis was shifting from static structural description to process and functions and experimental physiology rather than descriptive biology in a phase of the history of plant study here reduced to the expression ‘plant science.’

The post World War II academic Great Acceleration inevitably broadened the scope of plant study as the plant-human and plant-environment relationships were drawn into the academic arena. Technology had vastly extended experimental capacity at both the micro- and macro- scales. In the 1950s the cracking of the genetic code in DNA heralded the proliferation of new disciplines related to molecular biology and the sudden profitability of global-scale biotechnology. A 1960s gathering awareness of human impact on the biosphere spawned a plethora of environmental studies at the macro scale. The importance of genetic engineering at the micro scale now stood alongside concerns about the loss of biodiversity, sustainability, and climate change. Plants were integral to all these matters but in a very different and more complex relationships than had traditionally been addressed by academia.

The flow of new academic subjects that had accelerated in the 19th century was now a flood as the former set of relatively discrete topics increasingly resembles the knowledge web itself. On the one hand this expansion of subjects, a form of specialization, has increased the distance between disciplines and facilitated the formation of academic silos. On the other hand, the diversity of available academic pursuits has created the need for inter-and multi-disciplinary studies to unite whole sectors of that web. Broad-based topics of the 20th and 21st centuries include biodiversity, sustainability, the biosphere, climate change etc. Plant study is itself now intimately associated with many disciplines including ecology, biochemistry, information science, statistics, genetics and their associated technologies.

It seems that we are turning a corner in the mode of explanation we are using to understand the natural world. Up to the beginning of Informatia the approach was mostly analytic as academic subjects budded off their predecessors, fragmenting into ever smaller units of collective learning ripe for further analysis. But all these smaller units are nodes in the knowledge web with science now needing a phase of synthesis to explain its connectivity.

The history of academic plant study provides is an excellent example of this historical path. For about 200 years, from around 1550 to 1750, it was focused on plants themselves and their description. Interest in plant kinds and their structures shifted to research into process and function that reached a peak in the mid 19th century with the German publication of botanical text books beginning with cytology and and leading to the new findings of experimental (rather than descriptive) science. By the beginning of Informatia the major mysteries of plant structure and function were resolved and plant study was now looking beyond plants themselves to plant relationships to other parts of the natural world, notably humans and their wider environment – explaining the role of plants within the overall web of knowledge, and especially their role in addressing the global problems of the day such as climate, change, sustainability, and human influence on the planetary cycling of life’s essential ingredients: carbon, water, nitrogen, phosphorus, and oxygen.

Academic disciplines

Today when we speak of plant classification, we are inclined to think of scientific plant classification, the project that began in earnest in 16th century Europe. This was part of a phase of descriptive botany as a study of plant kinds and their relationship to one-another, a (possibly necessary) precursor to the extended study of other plant properties and relations that slowly gathered momentum in the 17th centuries to reach a peak in the German physiology of the 19th century when British botanical resources were strongly directed towards compiling an inventory of the plants under its colonial control.

Even including the studies of plant physiology, reproduction, anatomy etc. and the 19th century extension of science into agriculture and other developments, the formal study of the relationship of plants to their wider environment was a late starter and is still poorly defined in the terms of academia, while the relationship between plants and people remains a hotch-potch of loosely connected ideas.

Recognizing that plants are related to the world in many ways, only one of these being their relationship to other plants, perhaps the fact that these other major plant relationships have not been recognized by academia is simply a quirk of history, a function of the way that the evolution of academic disciplines played out historically.

It is unlikely that new academic subjects will arise now but we can examine the path that they might take so that some headway may be made.

The path of development of plant science followed, in broad terms, the path of establishment of all academic subjects.

The following loose account of what it is to be an academic discipline can serve as a template for a more organized approach to the study of plants in relation to people, and plants in relation to their wider environment.

An academic discipline is a domain of accumulated specialist knowledge with theories, concepts, and research methods that promote problem-solving by reducing complexity and organizing informational content. This usually includes the establishment of a formal technical nomenclature and clearly defined categories, properties, and relations. Social authority and respect for the discipline then comes with increase in number of its associated professional associations and academic institutions. This, in broad terms is how descriptive botany, as the study of plant kinds emerged from medicine in the mid 16th century, expanding into wider plant studies in the 18th and 19th centuries.

Plants & people

Though the relationship that exists between kinds of plants has been the subject of intensive academic scrutiny in the general study of the classification of the natural world, there has been no parallel investigation and schematization of the relationship between plants and people. – undoubtedly because this would appear a highly contentious project. But, even acknowledging this problem, the attempt would nevertheless provide a valuable focus of thought for future discussion. It is an exercise in classification.

What is required is an ontology (as understood in computer science/information science): the representation of a domain of knowledge using a formal nomenclature and definition of categories, including their properties and relations. This is the historical path followed by all academic disciplines: it promotes problem-solving by reducing complexity and organizing informational content.

Then there are the formal plant classifications produced by professional plant academics.

The number of plant categories we use has undoubtedly increased over time, largely in response to the historical increase in social organization, globalization, and a written record that allows us to store and develop our thought. By combining our knowledge of history with our specific knowledge of plant relations and the historical proliferation of plant categories it is now possible build a simple outline of the historical development of plant collective learning: not as a sequence of events, but as a history of ideas.

Scope

Explanations are easiest to follow by first establishing a general framework before embarking on a more ambitious program.

One point of departure might set historical boundaries within the categories of space and time. The space is Earth and the timeframe from, say, the origin of genus Homo about 2 million years ago to the present. The special interest is in the reciprocal factors of the plant-people relationship that have had a historical influence on the physical distribution of plants and people over the surface of the planet.

The categories chosen as historically significant (and worthy of closer investigation) are a matter of both empirical investigation and interpretation.

This is a contentious matter. There are clearly many interests – but perhaps a place to start is with the ways that plants and humans have most profoundly impacted one-another. This question cannot be answered by a method – we must simply determine (as far as possible) those relationships between humans that are (and have been) the most important. This is a complex question that can be framed in many ways. I offer the following as a point of departure:

plants as a source of energy
plants as food, drink and its additives
human manipulation of plant genetics

It there a method for approaching this problem?

n its most general form this is a question about the relationship between plants and people as it has played out over space and time. One method is to take a historical approach that takes a wide view of plant and human history, then narrows down the ranges of interest.

Scope of the project

Plant relations

Before we begin we need a clarification of the kinds of plant units that are to constitute the operational units of any classification we might devise.
The number of possible relations between plants and the world seems limitless. So, we are immediately confronted with a question akin to the metaphysical question concerning the classification of the universe: ‘How are we to classify the many ways that plants can be classified’?

From our study of the nature of taxonomy and classification we now have an answer to this question. If classifications are derived for a purpose/reason then the kind of classification we create depends on what we are trying to achieve: it depends on the particular interest.

Plant units

Classification must be classification of ‘something’. Is the ‘something’ simply a question of the units required to satisfy the purpose of the classification (e.g. a distinction based on size that might contain trees, shrubs and herbs)? But is there a plant unit out there in the world that can be used as a basis for most of our classifications – a plant unit that is, as it were, independent of human judgement?

Certainly, communication about plants depends on the delimitation of plant kinds. Classification must have something to classify regardless of the reason for the classification. Discrimination of plant kinds can be a matter of life and death when we consider the plants we can eat, those that are poisonous, and those that we can use as medicine, or for our clothing. 

So, plant classification must begin with the discrimination of plant kinds because these are the units of all plant classifications regardless of their purpose. However, here it must be remembered that the classification units selected might also vary with the purpose of the classification. The units being classified may not be ‘species’ but more general plant categories such as genera, vegetation types, herbs, perennials, bulbs, or grasses.

The salient point here is that most of the plant classifications we use in daily life are not so much about the plants themselves, or how one plant is related to another; our primary concern is with the way they can be used for human benefit. It is these other reasons, rather than curiosity about the plants themselves, that has determined that aspect of human history involving plants and, indeed, the historical path taken by plant science. Understanding this historical context can therefore help us plan for the future.

Three major kinds of plant relationship can be broadly recognized as being important for both human history and the history of plant science: that between plants and people; between plants and other plants; and between plants and their environments. We will examine the historical development of each of these broad relationships asking why the formal study of plants followed the particular path that it did. Also, how these three broad categories may be used to assess the needs that confront Informatia.

This account will briefly summarize the advance of plant collective learning by the multiplication of categories used in plant classifications. There are two trajectories of interest: that of everyday classifications, and that of followed in the course of the history of plant science including their intersection.

Scientific classification

Classifications, as patterns of relationship, are representations that help us explain and understand the world around us. Like all explanations, they proceed by abstraction and reduction – by simplifying complexity. The categories of ‘mentalese’ framed in our minds are structured in an intuitive way that is then communicated through language. Remember Pinker’s illustration of the way simple everyday language, that we all understand from an early age, provides us with a metaphorical representation of the way the world works by providing us with a crude intuitive physics?^[2]

The physical world

One key feature of scientific classifications is that they try to represent, as best they can, not human concerns, and the relationships between ideas in our heads, but the relationships between physical objects in the world outside our minds.^[1] We are tempted to say that the purpose of scientific classifications is to represent ‘the world as it really is’– but this would be more a figure of speech than a serious proposition.

Philosophers speak of science as dealing with natural kinds, as categories that reflect the character of the natural world rather than the subjective intuitions and interests of human beings. So, for example, science treats the biological classification of organisms as our best possible representation of these kinds and their relationships to one-another.

Though we have clear idea of what constitutes an individual plant, the foundational biological notion of a species is more controversial, a step into the realm of more abstract ideas. Are species ‘real’ entities existing in nature, or are they creations of the human mind – or both?

All scientific categories are subjected to rigorous intellectual scrutiny, not just the kinds of biology (as different sorts of organisms) but the methodology, language, logic and more. It is this rigour of reason that gives science its predictive strength.

Classification & progress

What is special about scientific classifications: why have they, among the many different kinds of classification, received academic attention?

The advance of science is not just about experiments, observations, and discoveries. It is also about the refinement of the web of ideas that provide our explanation and understanding of the world. Classifications help us to order and refine our thoughts more effectively and, when they are steadily improved over time, they make our interaction with the world more efficient and effective because they become part of our advance in collective learning. In this way they are progressive.

Not all classification is progressive. Going shopping requires all kinds of mental ordering of our purchases, but this is not making scientific progress. The advantage of science is that it uses shared and tested categories (not personal ones), categories whose refinement over time has occurred with the approval of the community of scientists.

Ultimately, scientific classifications help us to explain and manage the world by enhancing predictivity – but, in principle, their purpose/reason is to minimize human interpretation. That is, our improved capacity for prediction and understanding of the world is, as it were, a by-product of detached investigation, not its underlying intention.

Plant classification

This article is focused on the relationships of one key category plants. But, as we have seen in the first article, the relationships of plants can be expressed in a near-infinite number of ways. How are we to manage this complexity of potential relations?

Scientific special-purpose classification

Today, when we refer to ‘plant classification’ we are not referring to the many potential ways that we organize categories expressing plant relations. Instead, the expression ‘plant classification’ is usually applied in a restrictive sense to denote kinds of organisms. There is a foundational category unit, the species, and members of this category are then arranged into groups of both less inclusiveness, like the subspecies, and increasing inclusiveness, like the genus and family.

Before considering scientific plant classification in more detail, it may help to continue considering plant relations from a broad perspective.

For the purposes of this discussion, three wide-ranging and interconnected plant relationships may be recognised and all of which have, at some time in history, been the focus of human interest, including that of the educated or academic sector of society. These are, in broad terms: the interrelated relationships between plants and people; between plants and plants; and the relationship between .

Through history these relationships have been of varying interest and significance to both humanity and its academics, and each of these relations can be to focus of carefully constructed classification systems. In other words: just as the relationship between plants can be the topic for rigorous investigation and classificatory representation, so too can the relationship between plants and people, and plants and the environment.

Our understanding of this possibility will be assisted by a brief consideration of the historical role played by each of these relations.

Plants in relation to people

There is a sense in which all classifications relate to people since all classifications are generated by people and therefore reflect human interest – however detached it tries to be.

However, the focus here is on the primary purpose of the relations expressed in the plant classification – whether it is about human benefit (essentially the use of plants as a human resource or source of utility), or about the relations between plants, or the relations between plants and their environments.

Everyday classifications

The history of plants and humans is described elsewhere but it can be enhanced by understanding the historical diversity and proliferation of plant categories that have become available for everyday plant classifications and which were therefore part of the historical process of that is the accumulation of plant information as collective plant learning . . . the history of our ideas.

As history has unfolded, there have been three major transformations in the way we humans have thought about plants: three major ways in which plants have changed the mental landscape of plant categories available for classification.

Cultivation facilitated urbanization which brought with it those aspects of life we associate with civilization and a culture. Perhaps the most important intellectual distinction of human history was coming into focus: that between nature and culture.

We shall examine why the categories that we use today have not been subjected to the same intensive classification analysis as the category ‘species’. The ad hoc classifications of plant cultivation presented here relate to kinds of cultivation, and kinds of cultivated plants.

After about 10,000 years of plant cultivation we now recognize three major modes of cultivation: agriculture, horticulture, and forestry. There are many grey areas such as the relative taxonomic positions of floristry, market gardening, gardening (ornamental horticulture) and enterprises like orchards, vineyards, and plantation crops like rubber, pineapples, coffee and so on.

Cultivation is a commercial pursuit, so the ‘kinds’ (plant categories of commerce) are a hotch-potch of commercial epithets that make sense to us as consumers: wine, tea, cereals, fruit, vegetables, herbs, spices, timber, perfumes, medicines etc.

Within ornamental horticulture plants are grouped by many interests: perhaps those of a plant nursery that divides its stock into bulbs, conifers, perennials, fruit and nut trees, climbers, bedding plants, indoor plants etc.

These commercial categories, now familiar across the world, draw our attention to another momentous historical event that occurred between the 15th and 20th centuries, and which is now moving towards completion, and that is the globalization of the world’s biological resources.

Academic classifications

Historically the academic tradition of plant classification can be closely tracked following the written historical record that developed.

With the advent of hierarchically structured Bronze Age societies, powered by the food energy of cultivated plants, the opportunity arose for some members of society (often a wealthy or leisured class) to follow pursuits other than agriculture, manufacture, and trade. Supported by the rest of society these people provided ‘service industries’ that included a bureaucracy, organized religion, and education. This was a form of social organization that was administered by dedicated rulers, scribes, and priests. High social status gave their interests a special social significance and, since it was this class that maintained records, their interests were the ones passod on in an ‘academic’ tradition that was perhaps surprisingly divorced from the farming that was so necessary for the survival of all.

Human-centred

Plants in relation to people
The recorded plant interests Bronze Age city-dwellers, such as those in ancient Egypt, included a few ornamental plants (e.g. roses), plants that served as luxury goods (e.g. food enhancing herbs and spices), aromatic plants (e.g. the incense and other aromatics used to awaken the spirit world during religious observance).

However, by far the most interest in plants was directed towards their medicinal properties of plants that were often used in conjunction with incantations, spells, potions, ointments, inhalations, and other preparations used to alleviate physical and psychological discomfort. Most societies also used hallicinatory or other psychotropic plant products.

In ancient societies of both Asia and the West, probably as a result of religious priorities, it was the medicinal, aromatic, and food enhancing properties of plants that attracted the proto-academic interest of shamen and medicine mean of prehistory, of Natura, who were gradually replaced by the scribes and priests of Agraria.

The interest in plants was always utilitarian, driven by the ways that plants could support and enhance religious and daily life as a perspective that reflected the relationship between plants and humans, mostly in relation to their medicinal properties.

Plant-centred

Plants in relation to plants
A giant leap in the intellectual study of plants was taken in ancient Greece. This was the dawn of plant science as we understand it today when Theophrastus, who followed Aristotle as Head of the Lyceum in ancient Athens took plant study away from the central notion of them being a human resource.

Aristotle, a privileged and highly educated aristocrat who founded the Lyceum, famously declared:

‘How tiresome it is to keep asking of natural things – what is its use? . . . Once we have got what we need to survive, we should turn our attention to understanding nature in terms of its own ends and goods‘.^[7]

The great Aristotle-Theophrastus insight, then, was that plants could be studied for their own sake . . . their structure, function, reproduction, physical relationship to one-another, their interaction with their environments and more – simply out of curiosity and a desire to understand the world – without regard to human interests and economic concerns. Inevitably the categories and classifications that were used at the Lyceum reflected this relationship.

Botanical historian Morton summarizes Theophrastus’s contribution to descriptive botany noting that Theophrastus was aware that his fundamental distinction between trees, shrubs, sub-shrubs and herbs was ‘. . . one of convenience and not principle’. He (Theophrastus) spotted’. . . a whole series of characters which subsequently proved to have high systematic value’ including technical characteristics of flower structure along with ‘. . . a feeling for fundamental taxonomic groupings’. He ‘. . . treats related species in a manner closely corresponding to the modern distinction of genus and species . . .’.^[4] Many individual species described in the Enquiry . . . bear the hallmarks of ’. . . personal observation’ and are ’. . . masterpieces of botanical recording, of a quality and detailed accuracy not again approached in Europe for many centuries’. He also made ‘. . . conscious efforts to build an adequate descriptive terminology’ by coining a ’. . . copious vocabulary of technical terms, using existing words in combinations and senses new to the Greek language’.^[3]

This, so far as we know, was the first time that educated and recorded intellectual attention had become firmly focused on the relationship between plants and plants, rather than plants and humans.

But it lasted only briefly with Roman attention to plants bearing more on agriculture. With the collapse of the ancient world, academic interest returned to human desire for plant medicines. It would be nearly 1600 years after Theophrastus before the study of plants in relation to plants would return.

Middle Ages

With the collapse of the ancient world, the breakdown of trade routes, deterioration of monumental architecture, the loss of ancient learning, and the adoption of Christianity across Europe, social responsibility for education and caring for the sick fell to the monasteries.

But from the Renaissance to at least the mid 19th century it would be the naming, classification, description, and general inventory of plant kinds that would dominate the study of plants. Well into the European Middle Ages (and much later in Asia) the study of plant morphology and identification was motivated by plant medicinal use, herbals being the source of plant information for physicians, apothecaries, and the religious orders that occupied the monasteries that were now dispersed across Europe. Cultivation of plants, beyond their use as food, was in medicinal physic gardens with few having the time for plant ornament.

So, the scientific classification of plants was devised (in line with the original intentions of Theophrastus) to study the similarities and differences between plants themselves so as to organize them, as efficiently as possible, into classification categories based on their physical (morphological) characteristics.

The overwhelming goal of plant study during this period was therefore plant inventory: a scientific stocktake of the world’s plant resources – the kinds, their number, geographic distribution, and relations to one-another. All this was also strongly associated with utility and the possibility of economic advantage during the heyday of economic botany as the world’s major plant resources were distributed across the planet. This scientific endeavour was at its most pressing during the Ages of Discovery and Enlightenment when Europeans were mapping the physical boundaries of the world’s continents, no doubt an incentive to accelerate the inventory of the world’s biota. At that time the economic and cultural potential of the world’s unknown plant resource was of foremost concern. Plants like spices had made men fortunes and given some countries power over others.

At Theophrastus’s Lyceum in ancient Greece it became the relationship between plants and plants that became the key criterion of classification.

But this was a brief intellectual flame that was quickly extinguished for over 1000 years as the basis of plant study returned to the utilitarian relationship of plants and humans; classifications that characterized the post-classical world of materia medica, apothecaries, monasteries, and herbals that existed across both Europe and Asia.

After the Renaissance, as emphasis on comparative morphology increased, there was a return once again to the ancient Greek classification based on the relationship between plants and plants. This is a general approachto plant study that has continued, with decreasing emphasis, until the present day.

Bronze Age cities

With the arrival of Bronze Age cities came the development of writing with its enhancement of the potential for collective learning. This important addition to social life was overseen by a highly respected and educated class of scribes and priests. Though food and agriculture was central to human existence, the attention of this new academic class became focused on plants of medicinal and religious significance- the medicines, herbs, spices, and aromatics. The new educated class now focused on a reduced palette of plants whose selection criteria were based on luxury, religious and medicinal values. It was also this record that has come down to us through the ages as proto-botany rather than the agriculture and food plants that were managed by non-literate working people.

Regardless of the particular use to which plants were adapted, the ability to discriminate different kinds would doubtless have proved beneficial as methods of plant identification were incorporated into recorded collective learning.

Progress in plant identification was not rapid. It is estimated that the legacy of the classical world to the Middle Ages of Western civilization numbered only about 1000 species. Also, with the exception of a few brief years at the Lyceum of ancient Athens when Aristotle and Theophrastus focused their attention on plants themselves – their morphology, ecology, relationships, reproduction etc. – human interest in plants remained focused on their utility, the educated class still preoccupied with their medicinal properties.

So, up to the time of Greek science this perspective reflected the relationship between plants and humans, mostly in relation to their medicinal properties. Though it seems likely that plant use for foods would take precedence, it was the medicinal properties that comprised the specialized ‘scientific’ knowledge of respected community plant practitioners – the precursor ‘educated academics’ of old, be they the shaman, priest, or scribe.

At Theophrastus’s Lyceum in ancient Greece it became the relationship between plants and plants that became the key criterion of classification.

From about 300 BCE to about the middle of the 18th century plants were grouped together according to their habit as trees, shrubs, herbs and so on. The purpose of the classification was to group plants according to simple and obvious characteristics of the plants themselves rather than any particulFroar utility they might have for humans.Theophrastus’s division of plants into ‘herbs, shrubs, and trees’ was a practical classification that persisted into the 18th century. Today formal scientific classification groups plants in relation to one-another in terms of their presumed evolutionary (phylogenetic) history, sometimes known as phylogenetic systematics. The one-time morphological characters observable with the naked eye have been supplemented by microscopic and chemical-genetic information that is analysed using complex computer algoriths. Classification that concentrates on genetic characters is referred to as molecular systematics.

But this was a brief intellectual flame that was quickly extinguished for over 1000 years as the basis of plant study returned to the utilitarian relationship of plants and humans; classifications that characterized the post-classical educated world of materia medica, apothecaries, monasteries, and herbals that existed across both Europe and Asia.

Category ‘kind’

Scientific categories aim for maximum economy and precision in their expression and this begins with the metaphysical observation that we can consider the world of scientific objects in toto as consisting of kinds, their properties, and relations.

Among the multitude of categories of thought, emotion, and perception, are those denoting physical objects in the world. These can be referred to as ‘kinds’ and one subset of these kinds is that of the living organisms which constitute the community of life.

University botany

From about 300 BCE to about the middle of the 18th century plants were grouped together according to their habit as trees, shrubs, herbs and so on. The purpose of the classification was to group plants according to simple and obvious characteristics of the plants themselves rather than any particular utility they might have for humans. Theophrastus’s division of plants into ‘herbs, shrubs,subshrubs and trees’ was a practical classification that persisted into the 18th century. Today formal scientific classification groups plants in relation to one-another in terms of their presumed evolutionary (phylogenetic) history, sometimes known as phylogenetic systematics. The one-time morphological characters observable with the naked eye have been supplemented by microscopic and chemical-genetic information that is analysed using complex computer algoriths. Classification that concentrates on genetic characters is referred to as molecular systematics.

But this was a brief intellectual flame that was quickly extinguished for over 1000 years as the basis of plant study returned to the utilitarian relationship of plants and humans; classifications that characterized the post-classical educated world of materia medica, apothecaries, monasteries, and herbals that existed across both Europe and Asia.

Through the era of European printed herbals that lasted for about 200 years from 1470 to 1670, it was plant medicinal properties that took precedence, albeit diminishing, over the description of the plants themselves.

From around the 15th century the main task of botany had moved towards a global plant inventory, a task whose foundations had been largely laid by the European colonial powers in the mid-19th century at about the time of publication of ‘On the origin . . . ‘.

From about the mid-15th century into the mid-19th century the special study of plants was focused on the task of establishing kinds, what I refer to as ‘botany’. It is a narrowed-down focus of botanical attention (and therefore of classifications) to the delineation of plant kinds – to the way that we are to represent the different kinds and groupings of plants that exist in the world. This is what is at the heart of the desire for a global plant inventory.

In Linnaeus’s day the relationship was judged in terms of the overall similarities and differences between kind categories. This would indicate what were referred to as ‘natural affinities’. Classifications based on these plant characteristics (selection criteria) were then called ‘natural classifications’. However, it was often easier to group plants according to simple and obvious characters, like flower colour rather than overall similarity and difference. These classifications were called ‘artitificial classifications’. Linnaeus used a system of artificial classification based on the number of stamens and styles in the flower. He was aware that his artificial system would be superseded by natural classifications devised by botanists in France and England, but his method was simple and practical.

In Linnaeus’s day the relationship was judged in terms of the overall similarities and differences that would indicate affinities. Classifications based on these characters were called natural classifications. However, sometimes it was easier to group plants according to simple and obvious characters like flower colour, and these were known as artificial classifications. Linnaeus himself used a system of artificial classification based on the number of stamens and styles in the flower.

As plant knowledge rapidly increased during the 18th century this artificial system was further refined using a much larger set of characters. Emphasis was now placed on overall similarities and differences between the plants, rather than characters that were simple and practical to manipulate. This became known as natural classification because it grouped plants according to the way they seemed to be related in nature. Botanists were no longer imposing order on the plant world by using an arbitrary human choice of convenient characteristics, instead through the close examination of many characteristics they were discovering the order that existed within nature itself. Most botanists, like Linnaeus, believing that this was the ‘natural order’ established by god which they were gradually revealing.

The comparison of similarities and differences was sometimes referred to as a general-purpose (phenetic) classification since as many characters as possible were taken into account with no character regarded as more important than any other.

During the 18th century with a more universal terminology that included a broad range of plant parts, the selection of possible characters became more numerous as plants were further divided using a system of artificial classification which used just a few simple and convenient characters that facilitated plant identification to a finer resolution of taxa, as the number of plant species rose from about 1000 at the end of the classical era, to around 10,000 in Linnaeus’s day. The best known of these artificial systems was the ‘sexual system’ of Linnaeus which grouped plants according to the numbers of sexual parts in the flower. The selection criteria, though based on differences between plants themselves, were nevertheless practical characters of human convenience.

When Darwin published On the Origin of Species . . . in 1859, the meaning of ‘natural’ changed. Biological classifications became progressively focused on hypothetical evolutionary relationships, not just superficial resemblance. As it happened, those organisms with similar characteristics were usually closely related evolutionarily but not always, as in the case of parallel evolution. The selection criteria now became more focused on characters indicating common descent (hypothetical evolutionary trees now calculated by sophisticated computer programs using a wide range of characters) rather than simple similarity and difference. As it happened, descent with modification fitted in very well with the boxes-within-boxes strict nested hierarchy form of classification that had been used by Linnaeus.

Of all the various projects that might be subsumed under the category ‘study of plants’, up to the mid-19th century the key endeavour remained the process of inventory- the naming, classification and description of plants. This project has, unfortunately, dominated beyond all reason the study of plants and persisted into the present day. This was partly a consequence the preoccupation of the best botanical minds in Britain with recording of plants within its empire. But, just as botany reluctantly shook itself from the clutches of medicine, to descriptive botany has been slow to extricate itself from the wider relationships of plants, humans, and the environment. German botany began the fragmentation of plant study with major breakthroughs in plant physiology that were of consequence to agriculture, bringing plant study back into the world while the new ecology, the role role of plants within the environment as a whole, had also emerged in Germany with the work of Alexander von Humboldt, amplified by Ernst Haeckel.

We need to know the units that underlie any study, but the course of historyand its environmental concerns long ago outstripped the demand for taxonomy.

However, on the taxonomic front increasing numbers of characters were used to map, with ever finer resolution, the similarities and differences that existed between different kinds of plants.

The advent of computers and gene technology has subsequently given plant classification greater discriminatory precision, and therefore increased predictive power – all part of the progressive accumulation of plant collective learning.

While the selection criteria use to generate general plant classifications depended, very broadly, on three kinds of relationship: that between plants and people (by far the most common way that we have always grouped plants), plants and plants (as adopted by botanists and plant scientists), plants and the environment (as emerged with the scientific adoption of ecological ideas.

In the 19th century the project of plant scientists moved beyond the delineation and description of taxa into other fields of learning.

It remains to acknowledge that as a consequence of the historical development of of the study of plants of the many scientific plant classifications that could have been, the one we speak of as ‘plant classification’ is the one that organizes plant kinds. It is this path that we follow now, from its beginnings.

Carl Linnaeus

To take on the universal character of a science, plant study needed a community of plant practitioners to share a toolbox of scientific ideas – their own specialist academic realm – as a consensus of collective plant learning that could progress over time.

Before classification could proceed there needed to be an agreed set of basic biological units of classification (taxa), along with an agreed terminology for their structures, along with a method of inventory and description that included a system of nomenclature and classification. In the modern era it took over 200 years to develop these scholastic tools whose integration into an internationally-acceptable system was the great achievement of Carl Linnaeus. It was Linnaeus’s forging of this common scientific ground that constituted his great achievement, not just his reinforcement of the system of binomial nomenclature. The social conditions necessary for this to occur have depended on the technological development of transport and communication systems and increasing globalization.

So, it is hardly surprising that, in the toolbox of ideas needed to advance plant study, were the tools needed to determine (if possible – for all time, and everywhere) the plant kinds that existed in the world. Getting a consensus on how this was to be done would not be easy. It would require some agreement on, at least: a way to discriminate and organize plant kinds (classification); an agreed method for describing plants new to this scientific record (diagnosis), together with a simple method of designating kinds (nomenclature); agreed terms to denote their structures and other features necessary for the description of kinds (terminology); and an overall methodology for plant inventory so that lists of kinds could be amassed and understood anywhere in the world. All these conditions would have to satisfy the critical scrutiny of those who specialized in the study of plants before a new and universal science of botany could be claimed.

Though rudimentary plant science was evident in the Lyceum of ancient Athens, botany, along the lines described above, did not appear until the early modern period in Renaissance Italy when plant professors were appointed in university medical faculties and the business of systematic plant description took its first halting steps. However, it would be another 100 years into the modern era, at a time of European colonial expansion, before Swedish naturalist Carl Linnaeus provided a set of scholastic tools acceptable to the European botanical community such that it could be integrated into an international system of plant inventory. It was Linnaeus’s forging of this common scientific ground that was his great achievement, a small part of which was his reinforcement of the already-existing binomial nomenclature.

The new science would pass into Asia through the Neo-European colonies but It would be well over another century before this system of plant science would be accepted in non-colonial Asia.

So botany (treated here as scientific plant inventory as defined above) was developed as a scientific discipline in the West. Over time the pace of description of the world’s plants gathered momentum as the West extended its influence across the world, the rate of plant description reaching a peak in the 19th century as Western botanists worked on the floras of their colonial empires and beyond. Today this project, as a global inventory of ‘higher’ plants, is nearing completion.

Darwin & taxonomy

The classification of plant kinds was, at first, atemporal – concerned with the similarities and differences of known species without reference to time. It was assumed that God had created species in their final and immutable form. Linnaeus was a Christian who believed that his work was simply discovering the order (species) in nature that had been placed there by God (natural theology).

Time was introduced into the analysis of plant variation when Darwin. in his On the origin of species . . . (1859) suggested that the entire community of life had arisen by modification from a common ancestor. Biological species were not eternal and unchanging, they were subject to earthly evolutionary change. After Darwin, time would remain a crucial aspect of plant relationships. Similarities and differences now became evidence of ancestral evolutionary relationships (phylogeny) with God no longer a necessary source of biological order.

There had always been debate over which (or all) characters should be usied in assessing species. When determining phylogenetic relationships, some characters become more important than others. For example, vertebrates are, unsurprisingly, united in their branch of evolution by possessing vertebrae. The production of hypothetical evolutionary trees by computing characters (now often molecular) is known as cladistics, a system now employed throughout biology.

Through the history of the classification of plant taxa certain kinds of characters have been thought of as the key to a fully natural classification – whether they be those of pollen, chemicals etc. It would, however, appear that with the advent of genomics we are indeed approaching the final revelation of the ‘tree of life’ which includes some 350 plant families, and over 350,000 plant species.

although a profoundly different perspective emerged with the publication of On the Origin of Species . . .. Before Darwin, grouping were made based on morphological similarities and differences. Though this continued after Darwin, this took on a different meaning. Formerly similarities and differences were mostly treated as differences that arose when god created new and immutable species. This was essentially the view of plant classifications greatest exponent of these times, Carl Linnaeus. Humans, in their taxonomy, were organizing God’s creation.

Darwin presented a totally new account of the community of life as descent, with modification, from a common ancestor. Scientific plant classification, subsumed under evolutionary biology, therefore provides insight into the relationships of all organisms as they have evolved from a common ancestor. Closely related organisms possess similar properties and this becomes valuable knowledge in the establishment of predictability. Botanists now make a very clear distinction between artificial plant classifications such as those based on flower colour or edibility (a subjective classification) and natural classifications based on flower structures that reveal the evolutionary relationships of plants (much more objective).

Plant names

The two worlds of science and commerce reflect the ancient distinction between nature and culture. The core interests of academics and businessmen are different, so the reasons for their plant names and classifications will also differ.

In 1953 what is known as the Cultivated Plant Code was excised from the Botanical Code. This occurred in recognition of the tdiffering interests of two groups of people. The Botanical Code served the needs of classification botanists (taxonomists) who were concerned with the academic grouping of plants and the stability of the Latin component of their names. The Cultivated Plant Code provided non-Latin additional names useful in expressing plant variation that is useful in the world of plant commerce – to horticulturists, foresters and farmers.

The scientific classification of plants has itself fallen victim to conflicting interests between those who would like classifications to assist plant identification by drawing attention to obvious morphological differences between species (field characters), while experimentally-based botanists concentrate on genomics to represent past evolutionary relationships.

Plants & environment

People have always noted connections between environmental conditions and the kinds and forms of growth of vegetation – the influence of terrain, weather, interaction with other organisms and so on. However, it was only in relatively recent times that the study of organisms in relation to their environments acquired the status of an academic discipline. Ecology and environmental studies were latecomers to the academic agenda.

This was a late 18th and early 19th century development that began in the West as an adjunct to geography and it is associated with a golden age of German botany that included names like Goethe, Alexander von Humboldt. He selected as a key criterion of purpose and perspective, the relationship between plants and nature. This form of plant classification has been largely ignored or, perhaps better expressed as distinctly subsidiary and of little consequence for classifications based on plant/plant comparisons. In my view, this has had a profoundly unfortunate consequence for the history of botanical science as so much money and resources has been poured into plant systematics that could have been directed towards plant ecology and the attempt to better ascertain the scientific relationship between humans and the world’s vegetation.

The purpose of a scientific plant classification, then, is to mirror as accurately as possible what exists in the world. This, then, facilitates prediction and therefore the understanding and management of the objects it contains.

It turns out that the classification systems used in science are not unique to science – they are universal: they are the way we organize objects in our minds, and the way we organize them in our language. What then are the various ways of classifying things – what are their goals, structural properties, strengths and weaknesses?

Theophrastus’s division of plants into ‘herbs, shrubs, and trees’ was a practical classification that persisted into the 18th century. Today formal scientific classification groups plants in relation to one-another in terms of their presumed evolutionary (phylogenetic) history, sometimes known as phylogenetic systematics. The one-time morphological characters observable with the naked eye have been supplemented by microscopic and chemical-genetic information that is analysed using complex computer algoriths. Classification that concentrates on genetic characters is referred to as molecular systematics.

It is virtually impossible today to define what we mean by ‘science‘, but one devious way would be to say that it is the refinement of the classification of all those categories that we use in the field of activity that we refer to as ‘science’. So, for example, science is involved with the classification of physical objects like animals and plants. But science is much more than the classification of physical objects it also deals with more mental categories like names, laws, hypotheses, definitions, principles, theories and so on, and part of the scientific process is the refinement or improvement of these categories as well.

There are, then, three major phases of plant study: first, the close observation of plants in the general realm of human activity but especially through the specialist skills of medicine men and priests who had both knowledge and skills in the plant properties and their relationship to the spiritual world; second, a phase of plant inventory and description best described as botany; third, the expansion of studies beyond morphological and anatomical description into physiology and ecology as plant science.

By the mid-20th century the mysteries of plant structure and function were, in principle, resolved. The success of the human enterprise, not only in botany, was now becoming evident as an explosion in population with its associated consumption of nature. The world, much of which, at the dawn of the European Age of Discovery only a few generations ago, was wild and unknown, is now mostly converted to human use in an age we now know as the Anthropocene.
Our priority today is the gathering of information that will ensure that environmental damage bequeathed to future generations is minimized.

So, what are the important plant categories, plant classification systems (and their selection criteria) appropriate for the Anthropocene?

The categories we would use for such a classification would relate plants not to one-another, or directly to people, but to human environmental impact. But what would these classification(s) look like?

With the ‘tree of life’ near completion, scientific resources once devoted to taxonomy are now addressing other plant questions. The study of plants, across the world, emerged out of the use of plants for medicinal purposes.

Commentary

This article has discussed plant classification in a broad sense, as the way that we use plant categories to order plant relationships in the thought and language of our daily lives . . . not just in science, but also in our daily lives.

Academic classifications

Dating back to prehistory specialist plant knowledge has, until very recent times, been the preserve of a privileged educated class. This is a tradition that can be loosely traced from the shaman-medicine-man to priests, scribes, the wealthy elite of the ancient world to the dedicated academics of the universities of the Middle Ages and later.

Medicine

Plant classifications of the ancient world retained the former utilitarian focus on plant medicinal properties including their aromatic, food-enhancing, and psychotropic effects.

For a brief period in ancient Greece plants were studied for their own value – their structure, function, geography, mode of reproduction, and ecology. However, after the collapse of the classical world and social organization that supported an educated class, interest returned to plant utility and medicinal use, this persisting mainly in the new monasteries as centres of learning before the establishment of universities.

Herbals, physic gardens, & botanic gardens

This persisted through the age of printed herbals from 1470 to 1670, medicinal plants being the main feature of the popular physic gardens that developed in the cities and as adjuncts to the medical faculties of universities. The mid-16th century also saw the birth of botanic gardens in northern Italy, and it was in these institutions that most of the descriptive botany to follow would be carried out. Only at the beginning of the 17th century, and usually associated with the Leiden Botanic Garden under the great director Carolus Clusius (director 1593-1609) that botanic gardens extended their role from hortus medicus (medicinal garden) to that of hortus botanicus (botanic garden) by including plants of ornamental and other interest.

Gradually the discrimination of plant kinds was elevated in importance, resulting in the appointment of the first plant professors of early modern Renaissance Italian Universities. Plant medicine, as pharmacognosy, now followed its own separate historical path. In the West this marked the birth of plant study as a new academic discipline distinct from medicine and is often treated as the necessary botanical precursor to modern plant science that would come of age in the 19th century.

Descriptive botany

In a phase of descriptive botany that lasted for over 200 years the study of plants concentrated on the delineation of discrete plant kinds – their nomenclature, classification, and description as part of the process of plant inventory. The need for system and order in the plant world gathered urgency with the flood of plants into Europe following European colonial expansion across the world during the 16th to 18th centuries as a global plant stock-take became a realistic, albeit long term, objective.

It was Carl Linnaeus who provided descriptive botany with an internationally acceptable system of principles needed to create a scientific record the world’s vegetation. With this set of universal conceptual categories (mostly expressed in the universal academic language of Latin) that humanity had produced the universal descriptive framework for plant kinds that was the necessary foundation for the more wide-ranging plant science that would follow.

Plant science

Plant science came of age in the 19th century with the advent of Darwn’s On the origin of species . . . after which all biological science would, by necessity, fall under the general heading of evolutionary biology which included time and change within its key parameters of not only descriptive botany, but all biological science. But there was much more than this.

Science was now well entrenched in the universities whose studious application had spawned a proliferation of new academic disciplines facilitated by rapidly advancing technology. The specialist, restrictive and structural agenda of simple descriptive botany was now supplemented by venturing into new aspects of plant relations, most notably the elucidation of plant process and function using experimental studies that investigated plant physiology which some regarded as a move into true experimental science rather than mere description.

Historical trajectory

It is interesting to speculate (both history in general and the human-plant relationship) about the degree of predictability or ‘predetermination’ of historical events in history and the path of collective learning.

First came plant utility, the use of plants for food, medicine, structural materials and so on. With plants the common factor in so much of importance to human life and activity, the advantages of distinguishing one kind of plant from another were obvious. Though it was plant properties that were of primary interest (their key selection criteria) there were obvious benefits in being more proficient at distinguishing one kind of plant from another. In very general terms, the emphasis of plant practitioners had moved from the relationship of plants to people, to the relationship of one plant to another.

The need for plant ‘units’ served the same purpose as the need for units of perception, cognition, meaning, and language. It provided the means for linking, manipulating, and improving, our understanding of the relations between plants and the other categories our our understanding – the web of ideas that is part of our collective learning.

The study of plants had emerged from more general human activity in a process of naming, description, and classification – a phase of plant study appropriately known as ‘botany’ which emerged as an academic discipline in the mid-16th century.

Before Darwin, in the mid-19th century, botanists had noticed that plants shared similarities and differences and that they therefore shared different degrees of affinity with one-another. Even so, most people believed that god had created each species de novo as separate and immutable. The great Linnaeus believed that his work on plant classification in the mid-18th century was the revelation of plant order placed on earth by god.

In the mid-19th century Charles Darwin changed all this when he proposed that the entire community of life had arisen from a common ancestor. Modern classifications therefore seek to reflect, not only static similarities and differences, but also the dynamic changes that have occurred in the course of evolutionary history.

At the time of Darwin, plant study was beginning to broaden out once again as it linked once again to the human community. Agricultural science emerged stimulated by discoveries in chemistry and the new plant physiology, while plant description was putting a new emphasis on plant spatial distribution as new plants were drawn in from geographically distant colonial empires, and scientists like Alexander von Humboldt were initiating new scientific categories of plant distribution across the world and in relation to other environmental factors. The categories of ecology were now open to the process of collective scientific refinement.

The study of plants had entailed three core relationships: between plants and humans, plants and plants, and plants and their environment.

Key points

• Classification, in a broad sense, is the study of the relations between the categories of our experience and understanding

• Scientific classifications are concerned with categories that relate to the physical world and which have been scrutinized and approved by the scientific community

• Biological classification has, by convention, come to mean the grouping of organisms into categories of greater or lesser inclusion, with the category ‘species’ as a foundational unit

• Insofar as plant classification is an exploration of plant relations, three broad interconnected categories of relationship can be usefully distinguished, between: plants and people; plants and plants; plants and their environment

• Common usage of plant classification systems has always related to their utility – to their use as food and drink, structural materials, ornament, and so on.

• Historically, the formal study of plant classification has been determined by an academic or educated elite whose interests and concerns have changed over time

• Though the demarcation of plant kinds has always been a necessary aspect of plant classifications, it has not always been the focus of attention

• Historically, academic interest in plant classification was first focused on plant medicinal use. Briefly in ancient Greece attention shifted to the plants themselves – including not only their structure but function, geographic and local distribution, and relationship to their environment. In the European Middle Ages attention returned to plant medicinal use. By the 18th century the delineation of plant kinds had become critical as attention turned from local to global in the Ages of Discovery and Enlightenment when Carl Linnaeus provided the foundational principles for a universal plant taxonomy.

• From around the late 17th century, and partly a consequence of new technology, academic botanical interest widened to look in greater detail at plant morphology (e.g. anatomy), lesser-known plant groups (e.g. mosses, ferns, liverworts, and algae) and plant functions such as the mechanisms of reproduction and physiology. Attention was turning from structure to process.

• By the mid-19th century, under the influence of biogeographer like Von Humboldt and German plant physiologists, the study of plants had progressed from descriptive botany to an experimental plant science that incorporated plants in relation to people (e.g. scientific agriculture) and plants in relation to the environment (the beginning of academic studies in ecology).

• With the publication of Darwin’s On the origin . . . (1859) perception of life changed from one based on immutable species created by God, to one based on change over time as the entire community of life evolved from a common ancestor. The emphasis of plant classification now moved from the delineation of plant kinds (now well advanced) to the elucidation of their phylogenetic history.

• Today the project of ‘higher’ plant classification, as phylogenetic systematics, nears its completion in genomics and the inventory of tropical species. Attention has been progressively directed away from the relation between plants and plants, to the relations been plants and people, and plants and the environment.

• As global environmental concerns gather, we could examine more critically the classifications we currently use to relate plants to people, and plants to the environment.

Timeline

Plant Collective Learning

A distinction can be made between, on the one hand, plant collective learning as the totality of human knowledge related to plants and, on the other, to the learning that has been acquired as a result of formally organized science as practiced in universities, colleges and the like. The advance of collective learning may be viewed not so much in terms of the historical unfolding of events but more as the accumulation of concepts and words relating to these events and and closely related to the increase in complexity of social organization.

Everyday classifications tend to be local and regionally based although, with globalization there is an increase in the use of common categories.

Scientific classifications and categories have the strength of scientific consensus. Much of contemporary science began in the West but, like Western medicine, was increasingly adopted across Asia. Its potentially universal character has increased alongside globalization, social organization, and the advance of technology. Each new scientific discipline brings its own categories (principles, procedures, and terminology) that accumulate scientific knowledge. Many of todays’ academic disciplines had precedents in the ancient and medieval worlds. What is recorded here is the date of incorporation of subjects into formal academic studies since these are now within the international body of scientific knowledge. It is their international (global/universal) availability that makes them especially important.

Plant science (academia)

Development of plant science (research was not always within academia being often performed by private individuals but later incorporated in the body of plant scientific knowledge). Individual subjects were pursued to greater or lesser degree at different times and places. The timeline is a guideline only. A distinction is made between botany as descriptive plant inventory, and plant science based much more strongly in experimentation.

PLANT SCIENCE
First record of plant science – Lyceum under Theophrastus in ancient Athens

BOTANY – plant kinds, description, and inventory
16th Century
Mid-16th – establishment of botany as distinct from medicine with appointments of Professor Simplicium in Italian university medical faculties (Venice, Genoa, Bologna, Pisa)

17th Century
late 1600s – Anatomy – following the improvement of the microscope Italian Marcello Malpighi publishes Anatomia Plantarum (1671), the first major advance in plant anatomy quickly followed by Englishamn Nehemiah Grew’s An Idea of a Philosophical History of Plants (1672) and The Anatomy of Plants (1682). Grew made the crucial observation of plant cells (vesicles/bladders) and clearly identified and described flowers as the sexual organs of plants

18th Century

Early – Hybridization, sexuality, reproduction
Physiology (transpiration)
Mycology, bryology, lichenology
Mid – Linnaeus (establishes the foundations of botany as a collaborative scientific edeavour)
Late – Phycology
Physiology (photosynthesis, respiration)

19th Century
Early Plant geography
Microscopy of fertilization
Cell biology
Mid – Heyday of German plant physiology as experimental plant science with widely published and translated text books
c. 1850 – Biochemistry – (word first recorded in 1848) as an independent scientific discipline arose around the mid-19th century
1868 – Physiology – though Englishman Stephen Hales pioneered several aspects of plant physiology as outlined in his Vegetable Staticks (1727) it was, nevertheless, Julius von Sachs (1832–1897) who unified plant physiology into a distinct and important independent field of botanical study in his Lehrbuch der Botanik (1868)
c. 1910 – Genetics – The origin of genetics is associated with the work of Augustinian friar Gregor Mendel (1822-1884) but his work was lost for many years. Charles Darwin’s On the Origin of Species … (1859) records the theory of blended inheritance: offspring displaying a blend of parental traits. The word genetics was introduced in 1905 and only in the early 20th century did the subject find its way into universities

Cytology – cell biology was launched by Robert Hooke in the mid-17th century but would not find a place in formal theory until the mid-19th
Genomics – study of the structure, function, evolution, mapping, and editing of genomes.The first nucleic acid sequence was published in 1964, that of a gene in 1972, and the full human genome by the Human Genome Project published in 2004
Informatics – a word coined in 1956 witjh many meanings associated with various aspects of computation, information, and data manipulation
Proteomics – word coined in 1995 (derived from ‘protein’ and ‘genomics’) for the parallel study of the structure, function, evolution, mapping, and editing of proteins.

First published on the internet – 1 March 2019

. . . 2 July 2023 – minor update

Scientific classification.

The phylogeny of flowering plants as understood in 2020,
including the then recognized 435 plant families

The colors of the branches and the outer circles represent the major angiosperm clades (branches of the plant evolutionary tree) as indicated in the caption (ANA, Amborellales + Nymphaeales + Austrobaileyales). The illustrations around the circumference show 32 plant families and their position in the tree.

The flowering plants (angiosperms) arose in the Early Cretaceous about 145–100 million years ago, supplanting the earlier ferns and conifers (pteridosperms and gymnosperms). Palaeobotanical evidence indicates that this replacement was gradual, flowering plants not becoming dominant until the Palaeocene about 66–56 million years ago. The timing, geographic sequence, and plant composition of this diversification remains uncertain. There appear to have been substantial time lags, mostly around 37–56 million years, between the origin of families (stem age) and the diversification leading to extant species (crown ages) across the entire angiosperm tree of life. Families with the shortest lags occur mostly in temperate and arid biomes compared with tropical biomes. The ecological expansion of existing flowering plants, it seems, occurred long after their phylogenetic diversity originated during the Cretaceous Terrestrial Revolution.

Courtesy public domain license. Adapted from the originals provided by S.M., the Peter H. Raven Library/Missouri Botanical Garden and the Mertz Library/New York Botanical Garden