An Introduction to Botany (Volume 2) (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: BOOK II. PHYSIOLOGY; OH, PLANTS CONSIDERED IN A STATE OF ACTION. CHAPTER I. GENERAL CONSIDERATIONS. Plants have been thus far considered merely with reference to their structure. Our next business is to inquire into the nature of their vital actions, and to make ourselves acquainted with what is known of the laws of vegetable life. In explaining these things, it will be useful, in the first place, to give a summary exposition of the principal phenomena of vegetation, and then to support the statement by a detailed account of the more important proofs of all disputed points. In this the student will be materially assisted by the Physiologic Vtyitale of De Candolle, a work of which it is difficult to speak in terms of sufficient eulogy, but which may be justly described as the most important production on the subject of Vegetable Physiology, which, at the time of its publication, had appeared since the Physique des Arbres of Duhamel. I. If we place a seed (that of an apple, for instance) in earth at the temperature of 32 Fahr., it will remain inactive till it finally decays. But if it is placed in moist earth some degrees above 82, and screened from the action of light, its integument gradually imbibes moisture and swells; the tissue is softened, and acquires the capability of stretching; the water is decomposed, and a part of its oxygen, combiningwith the carbon of the seed, forms carbonic acid, which is expelled; nutritious food for the young parts is prepared by the conversion of starch into sugar; and the vital action of the embryo commences. It lengthens downwards by the radicle, and upwards by the cotyledons; the former penetrating the soil, the latter elevating themselves above it, acquiring a green colour by the decomposition of the carbonic acid they a...