Page:History of botany (Sachs; Garnsey).djvu/475

] According to Aristotle's view the plant itself was quite passive in the work of nutrition; since food was offered to it which had been already prepared for it in the earth, growth was to some extent merely a process of crystallisation unaccompanied by chemical change. In pointing to the formation of excreta Jung on the contrary ascribed a chemical activity to the plant, and by supposing that the organisation of the root was such as to prevent the entrance of certain matters and to favour that of others, he made the plant co-operate in its own nourishment, though he did not assume that it needed a thinking soul for this purpose.

Johann Baptist van Helmont, physician and chemist, and a contemporary of Jung, took up a position still more decidedly opposed to Aristotelian doctrines. He rejected the four elements of that philosophy, and regarding water as a chief constituent of all things he considered that the whole substance of plants, the mineral parts (the ash) as well as the combustible, was formed from water. Thus while Aristotle made the component parts of plants be introduced into them by water in a state ready for use, Van Helmont, on the contrary, ascribed to the plant the power of producing all kinds of material from water. It would scarcely have been necessary to mention this resistance to old dogmas, originating as it did in the notions of the alchemists, if Van Helmont had not made an attempt to establish his views by experiment; this was the first experiment in vegetation undertaken for a scientific purpose of which we have any information, and it was repeatedly quoted by many later physiologists, and employed in support of their theories. He placed in a pot a certain quantity of earth, which when highly dried weighed two hundred pounds; a willow-branch