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Aristotle, Plato’s pupil, concerned himself with the whole field of science, and his influence, especially during the Middle Ages, had a most profound effect on European thought. The greater part of his botanical writings, which belong to the fourth century before Christ, are unfortunately lost, but, from such fragments as remain, it is clear that his interest in plants was of an abstract nature. He held that all living bodies, those of plants as well as of animals, are organs of the soul, through which they exist. It was broad, general speculations, such as these, which chiefly attracted him. He asks why a grain of corn gives rise in its turn to a grain of corn and not to an olive, thus raising a plexus of problems, which, despite the progress of modern science, still baffle the acutest thinkers of the present day.

Aristotle bequeathed his library to his pupil Theophrastus, whom he named as his successor. Theophrastus was well fitted to carry on the traditions of the school, since he had, in earlier years, studied under Plato himself. He produced a ‘History of Plants’ in which Botany is treated in a somewhat more concrete and definite fashion than is the case in Aristotle’s writings. Theophrastus mentions about 450 plants, whereas the number of species in Greece known at the present day is at least 3000. His descriptions, with few exceptions, are meagre, and the identification of the plants to which they refer is a matter of extreme difficulty.

In various points of observation, Theophrastus was in advance of his time. He noticed, for instance, the distinction between centripetal and centrifugal inflorescences—a distinction which does not seem to have again attracted the attention of botanists until the sixteenth century. He was interested in the germination of seeds, and was aware, though somewhat dimly, of the essential differences between the seedling of the Bean and that of the Wheat.

In the Middle Ages, knowledge of Aristotelian botany was brought into western Europe at two different periods—the ninth and the thirteenth centuries. In the ninth century of the Christian era, Rhabanus Magnentius Maurus, a German writer, compiled an encyclopædia which contained information about plants, indirectly derived from the writings of Theophrastus. Rhabanus actually based his work upon the writings of Isidor of Seville, who lived in the sixth and seventh centuries—Isidor having obtained his botanical data from Pliny, whose knowledge of plants was in turn borrowed from Theophrastus.

The renewal of Aristotelian learning in the thirteenth century was derived less directly from classical writings than was the case with the earlier revival. From the time of Alexander onwards, various Greek schools had been founded in Syria. These schools were largely concerned with the teachings of Aristotle, which were thence handed on into Persia, Arabia and other countries. The Arabs translated the Syriac versions of Greek writers into their own language, and their physicians and philosophers kept alive the knowledge of science during the dark ages when Greece and Rome had ceased to be the homes of learning, and while culture was still in its infancy in Germany, France and England. The Arabic translations of classical writings were eventually rendered into Latin, or even sometimes into Greek again, and in this guise found their way to western Europe.

Amongst other books, which suffered these successive metamorphoses, was the pseudo-Aristotelian botany of Nicolaus of Damascus, which has acquired importance in the annals of western science, because it formed the basis of the botanical work of Albertus Magnus.

Albert of Bollstadt (1193–1280), Bishop of Ratisbon, was a famous scholastic philosopher. He was esteemed one of the most learned men of his age, and was called “Albertus Magnus” during his life-time, the title being conferred on him by the unanimous consent of the schools. The “Angelic Doctor,” St. Thomas Aquinas, became one of his pupils. According to legendary lore the name of Albertus would have been unknown in science, but for divine intervention, which miraculously affected his career. As a boy, tradition says that he was singularly lacking in intelligence, so much so that it was feared that he would be compelled to abandon the hope of entering monastic life, since he seemed incapable even of the limited acquirements necessary. However, one night, the Blessed Virgin, touched by his fervour and piety, appeared before him in glory, and asked whether he would rather excel in philosophy or in theology. Albertus without hesitation chose philosophy. The Virgin granted his desire, but, being inwardly wounded at his choice, she added that, because he had preferred profane to divine knowledge, he should sink back, before the end of his life, into his pristine state of stupidity. According to the legend, this came to pass. Three years before his death he was suddenly struck down, in the presence of his students, and never regained his mental powers.

The botanical work of Albertus forms only a small fraction of his writings, but it is with that part alone that we are here concerned. As already mentioned, his knowledge of botany was based upon a mediæval Latin work, which he reverenced as Aristotle’s, but which is now attributed to Nicolaus Damascenus, who was, however, a follower of Aristotle and Theophrastus. Although Albertus undoubtedly drew his botanical inspiration from this book, a large proportion of his writings on the subject were original.

The ideas of Albertus were in many ways curiously advanced, especially in the suggestions which he gives as to the classification of plants, and in his observations of detailed structure in certain flowers. We shall return to his writings in future chapters dealing with these subjects. It will suffice now to mention his remarkable instinct for morphology, in which he was probably unsurpassed during the next four hundred years. He points out, for instance, that, in the vine, a tendril sometimes occurs in place of a bunch of grapes, and from this he concludes that the tendril is to be interpreted as a bunch of grapes incompletely developed. He distinguishes also between thorns and prickles, and realises that the former are stem structures, and the latter merely surface organs.

Plate I

‘Sonchos’ [Dioscorides, Codex Aniciæ Julianæ, circa A.D. 500]. Reduced.

Albertus seems to have had a fine scorn for that branch of the science now known as Systematic Botany. He considered that to catalogue all the species was too vast and detailed a task, and one altogether unsuited to the philosopher. However, in his Sixth Book he so far unbends as to give descriptions of a number of plants.

As regards abstract problems, the views of Albertus on plant life may be summed up as follows. The plant is a living being, and its life principle is the vegetable soul, whose function is limited to nourishment, growth and reproduction—feeling, desire, sleep, and sexuality, properly so called, being unknown in the plant world.

Albertus was troubled by many subtle problems connected with the souls of plants, such questions, for instance, as whether in the case of the material union of two individuals, such as the ivy and its supporting tree, their souls also united. Like Theophrastus, and other early writers, Albertus held the theory that species were mutable, and illustrated this view by pointing out that cultivated plants might run wild and become degenerate, while wild plants might be domesticated. Some of his ideas, however, on the possibility of changes from one species to another, were quite baseless. He stated, for instance, that, if a wood of oak or beech were razed to the ground, an actual transformation took place, aspens and poplars springing up in place of the previously existing trees.

The temperate tone of the remarks made by Albertus on the medical virtues of plants contrasts favourably with the puerilities of many later writers. Much of the criticism from which he has suffered at various times has been, in reality, directed against a book called ‘De virtutibus herbarum,’ the authorship of which was quite erroneously attributed to him. We shall refer to this work again in Chapter VIII.

After the time of Albertus, no great student of Aristotelian botany arose before Andrea Cesalpino, whose writings, which belong to the end of the sixteenth century, will be considered in a later chapter. The work of Cesalpino had great qualities, but, curiously enough, it had little influence on the science of his time. He may be regarded as perhaps the last important representative of Aristotelian botany.