Philosophy of plant science

This article is an application of the reasoning developed in the article science to the study of plants. For an account of the history of plant science see Plant Science and for a compilation of the leading personalities in the world of plant science see Plant science people.

Philosophy, like other academic disciplines has, in the course of history, sired many children: what was one, is now many. So . . .  we have the philosophy of science, the philosophy of mathematics, the philosophy of history and so on. The philosophy of biology, as it emerged in universities, split off from the philosophy of science in the 1960s and 70s – but, as yet, there is no distinct philosophy of botany with its own journals and scientific community: its philosophical problems have been drawn into those of biology in general.

There is, however, one obvious botanical philosophically contentious question in the history and philosophy of science that deserves attention – and that concerns the historical origin and characteristics of plant science.

The study of plants

For most of us, most of the time, botany is the same as plant science – and both are simply and adequately defined as ‘the study of plants’.

But for the more fastidious there needs to be clarity: what do we mean by science and, depending on our decision, what are the special characteristics that distinguish plant science from other forms of science?

This article explores some of the topics examined in the article on science and the way these might be applied to plants.

Botanical works coming down to us from antiquity are few, essentially lists of plants, sometimes with brief descriptions, and almost always in relation to their medicinal use. It was Dioscorides (c. 40-c. 90 CE) who produced the encyclopaedic listing of medicinal plants that formed the basis of western plant knowledge for about 1500 years. His work was built on former compilations like those of Hippocrates and Theophrastus. Dioscorides referred to a plant tradition (botanikē paradoses) or botanical art (botanikē technē) whose practitioners paid close attention to the detail unlike the physicians Iollas and Heracleides. Dioscorides complains that these men provided medicinal prescriptions with poor attention to plant description.

Our modern world makes a distinction between ‘pure’ botany as the study of plants for their own sake – their structure, function and ecology – and applied botany as the study of plant utility, the many uses that we can make of them and, in the ancient world most extensively recorded as their medicinal uses.

It is, so far as we can tell, only at Theophrastus’s Lyceum in ancient Athens that the universal properties of plants were studied. Here the topic of study was all plants, not just those with medicinal properties or those that could be used in some way.  At the Lyceum plants were studied for their own sake. There is ample evidence for the recognition of two traditions – plant science, whose ‘father’ was Theophrastus, and pharmacology, whose ‘father’ was Dioscorides.

After the collapse of the classical world the study of plants would once again be restricted to those plants with medicinal properties.

In keeping with tradition, this web site distinguishes between the in-principle  universal study of all plants and all their properties. This does not exclude specialist studies (of, say, plant biochemistry or ferns)  but it does preclude deliberate restriction such as confining the study to only useful plants, or only those plants with medicinal properties. The point is that even botanikē technē would hardly qualify as science – or, at least, as science in an extremely weak sense.

Pure & applied: theoretical & practical

Hardy & Totelin in their book Ancient Botany^[7] (covering the period from the Homeric poems in the 8th century BCE to the 7th century CE with the advent of Islam and its scholarship) draw attention to the vexed distinction between pure and applied botany by translating Joseph Pitton de Tournefort’s (1656-1708) opening statement in Elemens de Botanique (1694) as ’Botany, the science that deals with plants, has two parts that one must distinguish carefully: knowledge of plants, and knowledge of their powers (virtues)’ and Tournefort recalls Theophrastus as the first plant scientist, and refers to Hippocrates the first physician. Tournefort clearly supports making a distinction between plant science (the study of plants themselves) and what we might call pharmacology (the study of their medicinal properties, powers or virtues). The distinction widens into the acknowledgement of a separation of the philosophical and utilitarian or practical aspects of plant study in educational institutions where applied botany is separated from plant science or botany in departments of agriculture, horticulture, forestry, floriculture, pharmacology and so on – what plant philosopher Edward Lee Greene referred to as ‘plant industry’. ^[8]

This distinction seems to be expressed in many forms and with varying degrees of  sophistication – roughly as follows:  there are those who go to university and those who are brought up in the school of hard knocks; there is the man of contemplation and the man of action; those in armchairs and those with shovels in their hands; there are refined and educated gentlemen and crude, ignorant labourers; those in protected ivory towers and those in the real world with their feet firmly on the ground; those who stay in the laboratory and those who do fieldwork; those with their heads in books and those engaging in experiment and observation;  those engaged in historia (enquiry) and those engaged in autopsia (personal observation); those using deductive logic to establish general principles and those using inductive logic applied to their observations.

Such an either/or distinction has its difficulties. The first modern-era botanic gardens – like those of Pisa, Padua, Bologna – were associated with the medical faculties of Italian universities with professors of botany and they were physic gardens whose attention to plants was of a medicinal nature. Botany, no doubt, entered the picture with the increasing attention to plant description, nomenclature and taxonomy but this was a gradual, not clear-cut, transformation. So there is a blending of the two ideas. At one extreme is the philosophical desire to explain natural phenomena through a general system of principles or laws that relate organisms to other organisms and the world in general – including what usually passes for ‘science’. At the other extreme are the more particular narrow, descriptive and practical aspects. By placing a strong emphasis on the former it might seem that for over 14 centuries, following Theophrastus, botany came to a halt before being revived at long last during the European Renaissance (Harvey-Gibson, R.J. 1919. Outlies of the history of botany. A. & C. Black: London.Morton, A. 1981.). Hardy & Totelin in their book Ancient Botany try to redress this idea by outlining the way that the literature of late antiquity and herbals does offer a ‘ . . . technical knowledge of plants, their names and morphology (form), their classification, their physiology, and their habitats’. They also make the important observation that Book 9 of Theophrastus’s Enquiry . . . was about plant pharmacology. There was a place for the utilitarian in Theophrastus’s botany.

Science historian David Wootton claims in his book The Invention of Science (2015) that

Modern science was invented between 1572, when Tycho Brahe saw a nova, or new star, and 1704, when Newton published his Opticks . . . there were systems of knowledge we call ‘sciences’ before 1572, but the only one which functioned remotely like a modern science, in that it had sophisticated theories based on a substantial body of evidence and could make reliable predictions, was astronomy, and it was astronomy that was transformed in the years after 1572 into the first true science . . . it had a research program with a community of experts.^[12]

Wooton, like Bacon during the Scientific Revolution, wants clearly defined boundaries. , he believed, had removed scientists from the more important activity of experiment and observation and the power of inductive logic. We can sympathise with his frustration, acknowledge his argument, and recognise that Aristotle made mistakes. But we also know that Aristotle was not just a theoretician: he made many close observations of nature that have stood the test of time. Perhaps it is better to see Aristotle as not so much a barrier to modern science as a stepping stone.

Plants & science

What is to count as plant science turns largely on what we mean by ‘science’ so lets look at three inter-related but slightly different approaches to this question:

1. Science is the application of logic and observation to the natural world – the most rigorous possible application of reason. On this view science has always been a part of human activity and was practiced by our ancestors in pre-history, albeit in a crude and undeveloped form.

2. Science is a mode of thinking; it is the use of deductive logic as a naturalistic empiricism that was devised by the ancient Greek philosophers, notably Aristotle, and applied to plants by his pupil Theophrastus.

3. What can justifiably be referred to as ‘science’ only arrived with the European Scientific Revolution and the ideas of people like Francis Bacon, Galileo Galilei, Rene Descartes and Isaac Newton which included extensive experimentation and the use of inductive logic in an empiricism that suggested that there was a special ‘scientific method’ as a common tool used by and whose results are shared by a community of scientists.

So, for example, the first view is expressed by botanical historian and philosopher Edward Lee Greene in Landmarks of Botanical History (1909):

‘Botany did not begin with the first books on botany, nor with the men who indited them, though every historian of the science whom I have read has assumed that it did. The most remote and primitive of botanical writers, of whatever country or language, found a more or less extensive vocabulary of elementary botany in the colloquial speech of all. The chief organs of plants stem, trunk, branch, leaf, flower, fruit, pod, seed, root, tendril, thorn and a multitude of others had been discriminated and named; the organs even known by all who had acquaintance with plants and trees, and the names were everywhere in use. Even the functions of several of the organs had been correctly ascertained before ever a line of botany had been written, most probably even before letters had been invented. The improvement of wild things by cultivation, the propagating of the newly acquired sorts of cuttings, by division of perennial roots and, in the case of trees, by grafting, are likewise arts that seem to antedate history; as do also the designating of different varieties or species that are evidently nearly akin, by two-fold names, one generic, the other specific or varietal’.

Greene makes the point that at least rudimentary terminologies, system, and empiricism were employed in pre-history and, insofar as these factors constitute ‘science’, then science was operational in pre-history. He states this more succinctly on page 7.

‘In the most extended use of the term, all information about the plant world or any part of it is botany. According to this view, all treatises upon agriculture, horticulture, floriculture, forestry, and pharmacy, in so far as they deal with plants and their products, are botanical. What many will consider a better use of the term is more restricted. In this use of it there will be excluded from the category of the properly botanical whatever has no bearing on the philosophy of plant life and form.

The second view is suggested by Spencer and Cross (2017) who emphasize another popular period in history offered as the starting point for science and that is Ancient Greece, in particular the carefully argued empiricism of Aristotle. In the case of botany this was the first drawing together of plant information into a coherent system of knowledge in a new discipline associated with an educational institution (the Lyceum) with a community of students who critically examined all findings. This body of botanical knowledge was written down in what amounted to the first botanical textbooks as lecture notes attributed to Aristotle’s pupil Theophrastus.

‘Theophrastus regarded many plant remedies, those based on hearsay rather than observation, with great suspicion. He was less concerned with the utility of plants – their human use as medicines, food, fibres and so on – instead his curiosity was focused on the plants themselves, their relationship to one-another, their classification, structure, function, reproduction, interaction with the environment, and geographic distribution. And always his knowledge was based on proven experience, reason, and logic. In fact Theophrastus’s approach hardly differed from that of modern evidence-based plant science. He clearly regarded gardens as potential places for experimentation and the close observation of nature.’

The third view is expressed by scientific historian David Wootton in his The Invention of Science (2015), the view that science arrived with the European Scientific Revolution:

‘Modern science was invented between 1572 … and 1704. There were systems of knowledge that we call ‘sciences’ before 1572, but the only one which functioned remotely like a modern science, in that it had sophisticated theories based on a substantial body of evidence and could make reliable predictions, was astronomy … the first true science. It had a research programme, a community of experts, and it was prepared to question every long-established certainty …’

Suffice it to say, here, that attempts by philosophers of science to establish a clear demarcation between ‘science’ and ‘non-science’ have proved fruitless. There were certainly watershed periods in history when what we now include under the label ‘science’ took large advancing strides, but establishing a precise and non-controversial boundary between scientific and other forms of knowledge has proved elusive.

Perhaps science is best regarded as proceeding in fits and starts, but gathering in complexity over time as society itself has become more complex and as more and more people are drawn into the ‘scientific’ community of shared knowledge, traditions, and practices leading to a progressive improvement in theoretical systems, principles, technical terminology etc., including the use of ever more sophisticated technology and communication.

Plants for human benefit & plants themselves

The distinction between plants as objects of human utility and plants as objects worthy of study in themselves is stated in its most  compelling way by the two ancient Greek philosophers Aristotle and Theophrastus. In one simple irritable sentence Aristotle, Theophrastus’s mentor, begins a new chapter in the history of science by resisting tradition and challenging the human mind to new possibilities.

He grumbles:

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]

Biology was born when Aristotle and Theophrastus decided to divide the living world into animals and plants with Aristotle beginning a systematic account of the former and Theophrastus the latter.

Plant science began with Theophrastus who, at the very outset of his Enquiry into Plants, responded to Aristotle’s request for an impartial investigation of the natural world by issuing a challenge to himself and future plant scientists . . . writing what was, in effect, a plant science manifesto.

We must consider the distinctive characters and the general nature of plants from the point of view of their morphology, their behaviour under external conditions, their mode of generation and the whole course of their life

The power of tradition and human self-interest is nowhere more clearly demonstrated than in the passing of nearly 2000 years during which Aristotle’s exhortation was totally ignored and human interest in plants was confined, once again, to medicine and pharmacology.

If you accept the statements of these two ancient philosophers, as I do, then we are left with the conclusion that there was no ancient botany or plant science (except in the Lyceum) only pharmacology.

When we look to the ancient world we are therefore left with two traditions: the pharmacology that is generally attributed to Hippocrates but traced back to Mesopotamia and prehistory, and the brief flame of enlightened plant science as practised by Theophrastus.

Revival of plant science

Aristotle had made a distinction between pure and applied plant studies. Natural scientists of the Renaissance were reminded of his words when, after being lost, Theophrastus’s works were published once again in the West in 1483 to once again attract critical minds that were trying to articulate what the the scope of plant study should be. Joseph Pitton de Tournefort (1656-1708) began his 1694 account of botany Elemens de Botanique with the words:

‘Botany, the science that deals with plants, has two parts that one must distinguish carefully: knowledge of plants, and knowledge of their powers (virtues).’

For botany itself we can look at the work of Georges Métailié, Emeritus Director of Research at the National Centre for Scientific Research who lectured in the field of ethnobotany for more than twenty years at the National Museum for Natural History in Paris. In 2015 he completed a 748-page treatise on the Chinese relationship to plants subtitled ‘traditional botany: an ethnobotanical approach’. This was just one volume in a series Science and Civilisation in China initiated by English academic Joseph Needham in 1954. It has become a monumental and continuing undertaking that has, so far, produced 27 volumes.

Needham was a biochemist, historian, and sinologist who wanted to account for the scientific dimension of the Great Divergence, the historical period after about 1500 when the West drew ahead of the rest of the world in political and economic power. He wondered why China and India had been overtaken by the West in science and technology despite being well ahead in the preceding centuries. He asked ‘Why did modern science, the mathematization of hypotheses about Nature, with all its implications for advanced technology, take its meteoric rise only in the West at the time of Galileo [but] had not developed in Chinese civilisation or Indian civilisation?’ After all, ‘Gunpowder, the magnetic compass, paper, and printing, which Francis Bacon considered as the three most important inventions facilitating the West’s transformation from the Dark Ages to the modern world, were all invented in China’.

Métailié was asked to complete the plant component of this grand synthesis by juxtaposing the Chinese experience of plants with that of the West, bearing in mind the development of Western science. It was assumed at this time that communication between East and West (either maritime or along the Silk Road) had been minimal leading up to the 16th century so this posed the tantalizing intellectual challenge of accounting for the independant cultural development of two separate plant traditions.

Needham had a clear vision of science as the accumulation of empirically correct knowledge about the world, tied together with ever more refined and tested concepts and theories. There was, he believed, a unity of science as it moved progressively towards a ‘truth’ about the physical world.

Métailié does not accept this characterization of science, taking an ‘anthropological’ view that is at odds with Needham’s vision. He does however broadly concur with introduction to the series by the general editor Christopher Cullen who wrote ‘the general study of animals [and plants] in their own right was simply not a recognised category of intellectual and literary activity in pre-modern China.’ According to Needham, botany as a science in its own right did not really begin in China until the mid-19th century or, Métailié claims, more accurately the second decade of the 20th century.

Métailié believes botanical science emerged as a discipline peculiar to the western world around 1600 and, through colonial expansion, to the rest of the world from about 1800. Before 1600 Chinese and European plant knowledge was comparable: expressed crudely it consisted of much empirical knowledge documented in vast herbals copied from sources dating back to antiquity – to Theophrastus in Europe and the Han Dynasty writers in China. It was the European Scientific Revolution that changed all this as it introduced new ways of thinking about and doing empirical investigations marked, at first, by a major systematization of plants, their nomenclature and classification. This was the beginning of modern taxonomy initiated by people like Englishman John Ray but forged by Linnaeus into a procedural methodology that became accepted by the European botanical community. This rudimentary Western science was soon transformed by the introduction of the microscope and other improvements in instrumentation. Métailié thus provides a history of Chinese herbals, continuing from earlier work in the series on botany written by Needham et al. (1986) and Bray (1984).

Modern students of the history and philosophy of science, as exemplified by Thomas Kuhn (and followed by Métailié) understand science as proceeding through a series of incommensurable theoretical paradigms (for example, though describing the same phenomena Einstein’s Theory of Relativity is different in kind – not just an advance on – Newtonian mechanics). Scientists may use empirical knowledge as their foundation but their major theories are clearly demarcated. Métailié justifies this for China by suggesting that little theoretical knowledge crossed to China on the Silk Roads even though plants did. A hint of Western botany probably arrived with the Jesuit missionaries of the 17th century but scientific attitudes to plants were, to all intents and purposes, absent until the mid-19th century.

The changes in thinking that arrived with the European Scientific Revolution are generally considered to be: the mathematization of empirical data; the move from Aristotelian deductive reasoning to inductive reasoning; the abandonment of organic metaphor and teleological explanation for mechanical explanation based on efficient causation only; and direct engagement with the physical world by laying far greater emphasis on experiment and observation. It should be pointed out that this approach was applied mostly to astronomy and medicine – its application to the nascent botany is a mute point.

Regardless, by 1700 a discipline called botany was part of the plant world view in Europe and it was considered different from (or in addition to) the previous shared form plant knowledge present in both Europe and in China. A community of botanists in Europe were developing a commonly-accepted system of ‘scientific’ nomenclature and classification that was supplementary to the common names and utilitarian classifications that had existed before. This new community of plant scholars developed their own rites, practises, microscopes, dissecting kits, and authoritative texts that examined not only names and classifications but theories about the way that plants worked, places of study that included herbaria for dried plants, and botanic gardens for living collections. These close-knit communities of like-minded academics were integrated with an extended corresponding community taking a similar approach to understanding the wider natural world.

The bone of contention is whether the plant knowledge that existed in China, and in Europe before the Scientific Revolution, should count as ‘botany’ (and whether this is the same as asking whether it should also count as ‘science’). Métailié settles for ‘ethnobotany’.
Métailié shows that, not surprisingly, the Chinese had plant theories as well as systematic plant knowledge that was recorded and interpreted. The degree to which pre-16th century similar plant theories in East and West were a consequence of exchange along the Silk Road is still contentious.

The shift in scientific paradigms so widely vaunted in physics and astronomy do not have their equivalents in botany (not to the same marked degree anyway) where there seems much more continuity with the past. Does this mean perhaps that botany is not really science? Recall the description of botany by a physicist as ‘mere stamp collecting’?

In defining science we walk the tightrope of, on the one hand, indefensible particularity and, on the other, useless generality. We must try to crystallize in some the way the fact that what we call ‘science’ has undoubtedly achieved momentous results. It won’t do, for example, to describe it as theory-based ordering of empirical knowledge. Nor can we define it succinctly as a unique methodology based on hypothetico-deductive reasoning.

Part of its strength is the use of high technology from simple microscopes to atom-smashing particle accelerators, together with the tool of mathematical modeling, and an acceptance of the possibility of error and improvement – of falsification. Somehow all this got underway between 1600 and 1800. If it is ‘Western’ then within this word we must include the rich intermixing of Near Eastern science.

There is still much to learn and much we will never know about the exchange of ideas in prehistory.

Also, we might balk at describing one system as being ‘better’ than another. There are simply different systems designed for different purposes and we should leave it at that. But this is to adopt an attitude more common to cultural studies. It denies the very essence and strength of science which is constant refinement and improvement based on evidence and results. Science is not relative: we only have to compare the world in 1400 with that of today to understand that. We might not approve of its influence but it is an influence of staggering dimensions that would have been inconceivable to citizens of that earlier world.

The study of plants, once known as botany, is today more frequently referred to as plant science. But to describe plant science as ‘the study of plants’ is uninformative: what exactly is plant science – what kinds of study and activity lie within its domain? If the study of plants warrants a special term then we assume there must be something about that study that is distinctive and special but that seems difficult to define. Perhaps the words have no meaningful content other than to convey the message that ‘We take plants seriously’, a couple of words that look good in a university handbook.

If plant science does have some special distinguishing characteristic(s) then that specialness is suggested by the word ‘science’. So what, then, are the defining characteristics of a ‘scientific’ study?

Ajania pacifica
Silver & Gold Chrysanthemum
Japan
An example of pattern in nature.
Growth tips of a single plant, each tip superficially identical to the others but in fact slightly different
Photo: Roger Spencer

Current thinking in the philosophy of science suggests that although science has a number of well-accepted procedures (use of observation and experiment to test or falsify hypotheses, the formulation of general principles and laws, maximization of predictivity and so on) these cannot be claimed as being unique to science, even in combination. Contrary to popular belief and much intellectual scrutiny we have found that there is no scientific method, procedure, or unique form of logic that separates science from other modes of thinking and behaving so, at present, we must define science in a seemingly unsatisfactory or indefinite ways as, say, ‘the domain of activities, principles, procedures, and knowledge that we associate with the word ‘science”, or maybe ‘the most rigorous practical application of reason that we can muster in the analysis of the physical world’ (see Reason & science). For simplicity we can define science as a domain of knowledge and plant science that part of the scientific domain concerned with plants.

Science as progressive and cumulative knowledge
One useful way of thinking about science is as a form of progressive and cumulative knowledge. Science is progressive because new scientific knowledge helps us to map the physical world around us (and within us) in ways that allow us to manage it more effectively in practical and predictable ways, and it is cumulative because it is a body of shared knowledge that builds on the shared knowledge of the past. This is not unique to science but it give us an insight into the way that certain kinds of knowledge develop.

Categories of knowledge
In order to operate in the world we break it up conceptually into meaningful units, categories, or concepts (see classification). We use these categories to ‘map’ the physical world in ways that help us to understand, explain, and manage it in more effective ways. There are a number of categories that have proved particularly useful in the domain that we call science: they vary in degree of abstraction and include the names of objects and structures, the analysis of functions, definitions, classifications, principles, theories, laws, pictorial representations, and so on. If we refer to these elements of scientific knowledge as ‘categories’ then it is clear that science becomes the progressive and cumulative refinement of the categories that we use to understand and explain the physical world.

To gain a better understanding of the domain of plant science we can now trace the progressive and cumulative historical refinement of its knowledge categories.

The units of study: parts and wholes and their names
We take the physical components of the world for granted: the world consists of discrete physical objects like tables, chairs, planets, and olympic swimmers. But though regarding these as discrete objects we become ambivalent when we consider their relationship to other objects because paradoxically they are, at the same time, both discrete wholes themseves while at the same being parts of greater wholes: here we have a cognitive dissonance – almost any object is both a whole and part at the same time. A chair is a whole with legs as parts, but when we consider a room, the chair is not the whole but just a part.

When we consider the plant world in its totality today we think of ‘wholes’ as large as forests or as small as chloroplasts. In the continuum of wholes and parts should we consider any particular whole as more important than any other and, if so, then why? This matter will be discussed later under plant classification but for the time-being let’s look at the historical way that humans segregated the plant world into discrete units.

Prehistory
No doubt in prehistory both individuals and small bands of people recognised and named many more plants than most of us would recognise today. This is because they were totally dependent on the plants in their immediate environment. Though we are equally dependent on plants today our need for practical plant knowledge is much less because the plants we use for foods, medicines and materials of various kinds are supplied in quantity and variety by other people without my need to becomes involved in any way. I do not know how or where the vegetables I eat are grown and have no idea what plants are needed to produce the medicines I take. Much of the plant knowledge of our prehistoric ancestors would have been passed on by oral tradition but it was only with the advent of writing that this knowledge could be shared with a wider group of people and supplemented with additional names that could be passed on to future generations. Though small groups of people might build up a large bank of plant knowledge this knowledge could only become of permanent value when it was shared reliably within large communities. This situation only arose with the creation of stored written records which in their early days were probably far inferior to the oral knowledge of their times.

What were the plant units that were named? Though vegetation could be grouped and classified in many ways there were practical units – similar-looking plants that had always displayed similar properties when eaten or used in some way. The degree of discrimination of ‘kinds of plant’ would probably vary according to circumstances but we can tell from the earliest written records and anthropological reports that plants were almost always divided into general groups and then divided again more finely. So there were trees like oaks and eucalypts and within that broad group could be discerned smaller units. This is a virtually universal characteristic of folk taxonomy and as akin to the way humans often discriminate between themselves as being within a broad group or family, say the Smith family, but a particular individual within that family, John Smith. Science has taken over the practical units of folk taxonomy and used the terms ‘genus’ and ‘species’ to denote the two groups. Genus and species are a powerful combination because in just two words it is possible to summarize both likeness and difference.

Early civilizations
So, only with the advent of writing could there be reliable, widespread, progressive, and cumulative plant knowledge. Though edible plants would always have been important, along with the skills to to distinguish between them, it was medicinal plants that became the subjects of study by medical experts, the physicians, in early civilizations. Medicinal knowledge had the power of life and death and was maintained, often in writing, by a priestly and academic class having religious and spiriual powers like the shamen and medicine men of prehistory. Those working in the fields would have been uneducated so the first European written records of plants that date back two to three millennia BCE consist of lists of medicinal plants written on papyrus, sometimes with descriptions of their medicinal properties.

Theophrastus, the father of plant science, who lived in Classical Greece in the fourth to third century BCE, wrote the first scientific accounts of plants incuding the names of many that grew outside Greece. During the period of the Roman empire an encyclopaedic list of plants was assembled by Pliny the Elder and a herbal or list of medicinal plants was also written by Dioscorides, a Greek soldier in the Roman army. Dioscorides’s Materia Medica and the earlier lists would become much copied into the European Middle Ages supplemented by plants known to the Arab world. Through the early Middle Ages even through the early days of printed books called Herbals, the legacy of known plants from antiquity and these times numbered no more than about 1000. Though we are familiar today with two-word (binomial) names like Jack Smith, such names were not used for plants until the eighteenth century. Up to that time it was conventional to use brief descriptions called phrase names.

Numbers
See also People of plant science
In the wild
Shared written knowledge of plants could only be useful when the plants discussed could be recognised within a community of people having plant knowledge. Accumulation of this kind of knowledge was, in retrospect, extremely slow. Lists of plants dating back to the ancient civilizations of Egypt and Mesopotamia name about 250 different kinds of plants, many of these are recognizable today, while the two botanical tracts written by Theophrastus list 450-550 different kinds. A famous list of medicinal plants, a Materia Medica, was compiled by Pedanius Dioscorides, a Greek soldier in the Roman Army and this would serve as the basis for works of the Middle Ages up to and including the first printed books known as Herbals that continued into the seventeenth century. A vast encyclopaedia of the Classical world, Historia Naturae, was written at the time of the Roman Empire by Pliny the Elder and though it included quite a large section on plants it was largely compiled from earlier works adding nothing original.

By the end of the fifteenth century intellectual curiosity, which had previously looked backward to the authority of classical scholars and the scriptures, was now looking forwards as botanists, excited by the new Age of Discovery, began to speculate about the possible number of different plants in the world. The herbals had described 500-1000 species, this being the legacy of Classical and Medieval knowledge^[1]. In 1613 Jean Bauhin (1541-1613) (son of Jean Bauhin (1511-1582) who was physician to Jeanne d’Albret, Queen of Navarre) described about 4000 species. Jean’s brother Gaspard, in the Pinax of 1623, increased this number to 6000, his account including synonymy, references, and binomials over a century before they were used by Linnaeus. English botanist Ray’s three-volume Historia Plantarum (1686, 1688, 1704) lists some 18,700 different kinds of plants. Linnaeus, more than any other botanist, was aware of the importance of ensuring that communicated knowledge about plants would be in a form that was accessible to the community of plant scientists. He vastly facilitated the arrangement of plants into scientific groupings, the means of presenting the host of synonyms that were beginning to appear, the construction of an agreed terminology for plant description and the mode of description itself, the standardization of binomial nomenclature and much more. Linnaeus in 1753, less than 40 years before Australian settlement, believed that the total number of plant species in the world was unlikely to exceed 10,000 (Stearn 1959).

By the nineteenth century botanists were once again entering a new encyclopaedic phase as part of the aspirations of European empires. One compendium initiated by August de Candolle, Prodromus Systematis Naturalis Regni Vegetabilis, attempted to include all known seed plants, classified and described in 17 volumes, the last 10 volumes written by other authors (35 in all) and published by his son Alphonse (1823-1873); it included 58,000 species organised into 161 families. Englishmen George Bentham and Joseph Hooker (Director, Royal Botanic Gardens Kew) produced a major natural classification of seed plants Genera Plantarum (1862-1883) with 200 families and 7569 genera described in detail.

The task of making a global inventory of plant species fell into abeyance until facilitated by computer database technology. Today, in 2016, the total number of naturally-occurring seed plant taxa in the world is estimated to be about 369,000.^[2]

A World Flora Online Project (Missouri Botanical Garden, Royal Botanic Gardens, Kew, Royal Botanic garden Edinburgh and New York Botanical Garden) was initiated in 2012 in response to Target 1 of the Global Strategy for Plant Conservation^[5] with a widely accessible working list of known plant species now completed in 2010 as a step towards a complete world flora and an aim to halt the loss of plant species worldwide by 2020: see The Plant List (www.theplantlist.org).

In cultivation
By the 17th century Europe’s leading gardens, where the world’s leading botanists worked, were competing to hold the greatest number of different plants. In the 1660s the Jardin du Roi in Paris claimed about 4000 species (Stafleu 1969), probably the most extensive at this time, but by 1720 giving way to Leiden under Boerhaave with 5846 different kinds (Boerhaave 1720). Between 1730 and 1770 both the reputation and collection at the Chelsea Physic garden grew until the species totalled about 5000 (Uglow 2005, p. 147). John Hills’s Hortus Kewensis of 1769, an inventory of Kew’s stock, listed about 600 species. Then, following the 1768 edition of Miller’s Gardener’s Dictionary came Aiton’s three-volume Hortus Kewensis in 1789, a monumental descriptive inventory of Kew’s living collections now under Banks’s influence totalling over 5,500 species. This was an invaluable horticultural record that included Linnaean Latin diagnoses (much of it was written by botanists Solander, Dryander and Brown) and annotated with dates of introduction etc. It included ‘… almost all the species then cultivated in England’ (Stearn 1961, pp. cvii-cviii). The 1813 edition of Hortus Kewensis had swelled to five volumes and over 11,000 species including about 300 from Australia, indicating the further impact of Banks’s acquisitiveness (Turrill 1959, pp. 20-21, 23-24; Drayton 2000, p. 125). The Berlin Botanic Garden, effectively founded by Karl Willdenow in 1801, by the time of his death in 1812, contained about 7,700 species.^[3]

In 2015 it is likely that more than 120,000 different kinds of plants (this includes cultivars) were being cultivated in British gardens (Armitage, pers. comm.), but it is not sure whether the total number is increasing or decreasing. In Australia the total is at least 26,000. The Royal Botanic Gardens Kew today cultivates 4,141 genera, and 11,557 species and the herbarium contains about 7 million specimens and over 95% of known flowering plant genera.<sup[4]

Structures
As more kinds of plants were recorded, and from more dispersed regions, there was an increasing need for improved descriptions that would help distinguish the different kinds, otherwise the lists of names would become useless. Having established a small core of different kinds of plants growing in dispersed regions of Europe it was now necessary to provide descriptions that would allow one kind to be sorted out from the others. If this could not be done then the potential shared knowledge that was embedded in lists of plants would have no general benefit. Plant identification thus required a mutually agreed system, or terminology, for plant structures.

Once there was an agreed list of different plant kinds together with an agreed terminology for plant structures then communication between plant people was greatly facilitated, including discussion of plant function.

Functions
Though there is ample room for disagreement about not only the names of plant structures but what constitutes a structure worthy of special recognition in a name in the first place. This situation is made vastly more complicated when we come to consider the aspect of dynamic change in plants. This is the aspect of botany where theory has been most evident. How do we explain all the life processes that go on in a plant, its morphological development and nutrition? This is an active area of research today. Among the breakthroughs can be listed theories accounting for germination, dormancy, transpiration, respiration, photosynthesis, hormonal control (tropisms and nastys), photoperiodism and circadian rhythms, seasonality.

Today we regard plant physiology as a process of reverse-engineering the unconscious purpose of plant function that is a consequence of natural selection.

The scope of plant science disciplines
Regardless of questions concerning the nature of plant science we need to examine what it is that people who call themselves plant scientists do, because one answer to our question about the meaning of plant science is that it is all those activities, principles, and procedures that are used by plant scientists.

One primary goal of science is the refinement of the shared categories we use to describe the physical world: this includes the basic units of study (named taxa or taxonomic groups, most familiar today as genera and species) and the way these groups are related to one-another, and the structures that these units possess (a standardised terminology for their parts wit ha greement on the parts that warrant categorization). As all organisms are functionally organized then part of the scientific process entails the understanding of these functions (see purpose). As an aid to communication it is therefore possible to provide improved descriptions of taxa and their relationships, including their structures and functions and in this way botanical science can be understood as both progressive and cumulative. It is progressive because it leads to a better understanding of plant structure and function with all the practical consequences that this entails, and it is cumulative since knowledge of plant structure expanded from simple morphology to encompass anatomy, cytology, physiology, biochemistry and much more. Botany, once one part of medicine, is now itself fragmented into myriad specialist disciplines including those dealing with particuar parts of the plant kingdom.

The scope of plant science(to be worked up)
Our minds process information by breaking it up into adaptively meaningful cognitive categories (concepts, units of representation) – what we can call cognitive segregation. To operate in the world we do not think about these categories all at once but arrange or classify them into convenient groups depending on our particular interest or concern – our current frame of reference – what we can call our cognitive focus. Our cognitive focus is mostly directed towards our perception, the physical needs of the moment, and tasks of the day. Science, however, focuses on the categories that map the physical world as accurately as possible through the theories, names, properties, definitions, laws and other categories that we use in the scientific enterprise.

As the number of items to be classified increases, so the classification itself tends to become more complex and finely resolved. Conversely smaller numbers lend themselves to greater simplicity. In the mid twentieth century the natural sciences were simply divided into four primary domains: Biology, Geology, Physics, and Chemistry. But the accumulation of knowledge in recent times has made these categories seem less distinct as disciplines have tended to merge more into one-another.

In relatively recent times bacteria and fungi have been separated from the plant kingdom and the study of plants divided into a large number of disciplines. Beginning with taxonomy we see the study of structure divided into external factors (morphology) and internal structures (anatomy), and physiology. From the ?17th people begin to specialize in particular segments of the plant kingdom, so we have bryology (mosses and liverworts), pteridology (ferns), phycology (algae), mycology (fungi). There is the specialist study of fossil plants or palaeobotany. Nowadays plant structure is the basis of specialist disciplines dealing with particular structures so palynology is the study of pollen and carpology the study of fruits. Ultrustructure (structures revealed by electron microscopy), taxonomy, morphology while ‘dynamic’ and developmental process are studied by physiology and embryology while advances in chemistry have made it possible to study processes occurring at a molecuar level through biochemistry. The advent of Darwin‘s theory of natural selection resulted in evolutionary biology or phylogeny. Former subjects like taxonomy have taken on modern techniques so that while taxonomy was once largely a matter of morphology (sometimes called alpha taxonomy), today we have molecular systematics, chemotaxonomy, cladistics, phylogenetic systematics, genomics, informatics. More applied disciplines like horticulture and agriculture are themselves subdivided into subdisciplinary categories and categories can intergrade to varying degrees as we consider hybrid categories like economic botany, phylogenetic systematics, horticultural botany and so on. Agricultural botany, and pharmacognosy. The principles and techniques of many modern disciplines are applicable across the biological world as is the case with genetics and pathology. At a more inclusive scale the role of plants within ecosystems has been addressed through the discipline of ecology.

The impact of technology
Technology, which is a product of science, has extended our perception of the world from that of our evolved everyday sense experience and plant characters or morphology evident to the naked eye, to include objects viewed at very different scales. The first major invention to impact on botany was the microscope which effectively opened up an entirely new world that required decisions about its own units of study, structures and functions. It was now possible to provide scientific explanations at a different scale as the discipline of cell biology (cytology) opened up, delving in even more detail with the invention of the scanning electron microscope with the structures and functions at a scale below that of the cell in discipline known as ultrastructure (fine structure). Rapid advances in organic chemistry meant that theories concerning molecular processes in the plant could be postulated in the new field of plant chemistry (biochemistry, molecular biology) and of special interest were the macromolecues of DNA found in the cell chromosomes that determined so much of the plant’s structure and function through studies known as genetics. The interpretation of the role of plants within world vegetation has beengreatly facilitated by computers, aerial photography, satellite imagery, GPS and the like.

New categories require new classifications that incorporate the new categories and which divide the objects being classified to a finer resolution.

Plant science

But what justifies the claim that plant science arose in the Lyceum in ancient Athens? Wasn’t the study of plants carried out here just an elaboration or extension to the plant listing, simple description, and medicinal and utilitarian literature that preceded this work?

Studies at the Lyceum must be set against the intellectual climate of those times when there was among those prepared to open their minds, a sincere attempt to maximise what today we would refer to as ‘objectivity’. This was the exercise of reason unfettered by communal or individual self-interest: it was curiosity for its own sake. This meant putting aside, as far as possible, the supernatural, mystical, traditional authority and tradition, and the teachings of charismatic leaders and the temptation to engage the creative imagination. This was the general tenor of the Pre-Socratic thought that predated work of Aristotle and Theophrastus at the Lyceum. This meant a greater reliance on observation and the growing belief that reason applied to careful observation could provide reliable knowledge – a realization of the power of empirical generalizations that has underpinned all subsequent science. Combined with the desire to apply reason to careful observation from a broader viewpoint came the desire for increased discrimination in all the categories of thought . . . a need to not only describe, but to engage in the attempt to systematize, classify, order and arrange, following a path of endless refinement . . . and to place all these categories within an overarching theoretical framework of ideas – the place of plants in the general scheme of things, in ‘reality’ – in another process of assessment that is also undergoing constant revision.

Theophrastus’s works are like a botany text books based on lectures whose content is under constant revision. The framework of ideas he uses amounts to the attempt to describe and explain as accurately as possible plant structure and function. As he advocates the establishment of general principles (empirical generalizations) he investigates not only particular kinds of plants at particular places and times but generalizes, where possible, to all plants at all times. Historia Plantarum is about plant morphology and classification including descriptive and economic botany – plant parts, their definition, composition, and relationship to other parts, while Causae Plantarum is, in effect, a manual of physiology, investigating plant growth and reproduction.

So, yes, the work of Theophrastus was an extension of what had gone on before but the degree of intellectual application, critical discrimination, terminology, empirical generalisation and categorisation was of a kind never recorded before and which has so much in common with practices known today as ‘science’ that the designation ‘plant science’ becomes a valid and worthwhile category.
However, if this is accepted then it becomes clear that plant studies preceding it (the plant lists and accounts of medicinal properties), and those following it, up to the modern era (slightly more elaborate the herbals and plant catalogues), can hardly qualify as plant science of the depth and range we see in Theophrastus’s works. ‘The slackening of interest in botany in Hellenistic and Roman times is witnessed by the gradual oblivion which buried the text of Theophrastus almost completely after the second century AD.’ P. 71 It was a failure of intellectual interest: something we can too easily overlook in our own times. There is a world of intellectual difference between the plant lists and brief descriptions that came before and after Theophrastus and the systematic method employed by studies at the Lyceum.

Key points

• The creation of mental categories that improve our mental representation of the surrounding environment may be regarded as one aspect of biological adaptation

First published on the internet – c.2020
. . . 1 August 2023 – minor editing