Schleiden, who had commenced his botanical labours with some important researches in anatomy and the history of development, the most valuable of which in matter and form was an enquiry into the development of the ovule before fertilisation (1837), composed also a comprehensive text-book of general botany, which appeared first in 1842-3, and in much improved editions in 1845 and 1846, and in two subsequent years. The difference between this and all previous text-books is the difference between day and night; in the one, an indolent carelessness and an absence of ideas; in the other, a fulness of life and thought, calculated to influence young minds all the more, because it was in many respects incomplete and still in a state of fermentation. On every page of this remarkable work, by the side of facts really worth knowing, the student found interesting reflections, a lively and generally coarse polemic, and praise and blame of others. It was not a book to be studied quietly and comfortably, but one that excited the reader everywhere to take a side for or against, and to seek for further instruction. The work is generally quoted as ‘Grundzüge der wissenschaftlichen Botanik,’ but its chief title is ‘Die Botanik als inductive Wissenschaft,’ which indicates the point on which Schleiden laid most stress. His great object was to place the study, which had been so disfigured in the text-books as scarcely to wear the semblance of a natural science, on the same footing with physics and chemistry, in which the spirit of genuine inductive enquiry into nature had already asserted itself in opposition to the nature-philosophy of the immediately preceding years. It may seem strange to us now to see a text-book of botany introduced by a formal essay, 131 pages long, on the inductive method of investigation as opposed to dogmatic philosophy, and to find the principles of induction set forth again and again in connection with a great variety of subjects in the book itself. Many objections may be raised to the contents of this introduction; it may be said that many philosophical dicta are misunderstood in it; that Schleiden himself has frequently offended against the rules there laid down, for instance, when he substitutes a formative impulse (nisus formativus) for the vital force which he rejects, which is only introducing vital force again under another name; that it is superfluous to present the history of development as a ‘maxim’ in Kant’s use of the word, instead of showing that the history of development enters naturally and of itself into inductive investigation, and so on. All this will not lessen the historical importance of this philosophic introduction; the traditional way in which descriptive botany was at that time presented to the student was so thoroughly dogmatic and scholastic, trivial and uncritical, that it was necessary to impress upon him in many words, that this is not the method of true investigation of nature.