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. [Illustration: _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.