Vegetable Physiology, 17 



VEGETABLE PHYSIOLOGY. 



HUM BER ONE. 





In order to obtain a correct knowledge of either animals or 

 vegetables, it is not enough simply to observe their outward 

 appearance, to examine their different parts superficially, to 

 mark the changes which they undergo, or to watch their habits 

 and motions. These are but the results of their internal struc- 

 ture, and before we can arrive at a right understanding of 

 them, we must become acquainted with that structure. Two 

 branches of science have for their objects the mechanism and 

 functions of the organs of animals and plants. Anatomy 

 explains the form, structure, and disposition of those organs, 

 and Physiology their uses and functions. In Zoology, the 

 distinction between these branches is more strictly adhered to 

 than in Botany, though in the latter science Vegetable 

 Anatomy or Phytotomy is properly a separate department 

 from Vegetable Physiology. We do not consider, how- 

 ever, that it is necessary here to specify the subordinate sec- 

 tions into which botanists have divided these sciences, since 

 the beginner is liable to be embarrassed and discouraged by a 

 multiplicity of terms, which he will better understand in the 

 course of his onward progress. We shall prefer, therefore, for 

 the present, to define Vegetable Physiology as that science 

 which explains the nature, appearances, and uses of the inter- 

 nal organs of plants. It will be necessary, of course, to exam- 

 ine the form and structure of these organs, before their func- 

 tions can be discovered. Let us take, then, almost any com- 

 mon plant, and see the parts of which it is composed. The 

 most obvious of these are the stem, roots, leaves, and flowers. 

 It will be seen, when we have advanced a little further, that 

 they are subdivided into many other parts — but for our pre- 

 sent purpose it is enough to mention these. The root, then, 

 whose office it is to fix the plant in its place, and to draw nutri- 

 ment from the soil, the stem which carries this to the leaves, 

 and raises them to receive light and warmth, the leaves which 

 elaborate this nutriment and make it fit for the sustenance of 

 Vol. II.— 2. 



