General Physiology of the Plant. 1 89 



elements of reproduction already given for the lily will, with 

 very slight modification, do also for the type now before us. 

 Repetition, therefore, is unnecessary. We have also directed 

 attention to the chief points in the embryology in connection 

 with that of the lily. We proceed now to give a brief ac- 

 count of the general physiology of the plant in application 

 (with exceptions which will be pointed out) to all the types 

 considered in the preceding sections. 



SECTION V. GENERAL PHYSIOLOGY OF PLANTS. 



As was pointed out in sect. i. of Chap. III. every organ in the 

 plant body has a special duty or function to perform, a duty 

 directly subservient to the welfare of the individual as a 

 whole. Just as we may consider the plant body as a whole 

 from a morphological point of view, so also we may discuss 

 the general physiology of the vegetal organism as a whole. 

 These two aspects may be denominated the statical and the 

 dynamical aspects respectively. Previously, however, to 

 entering upon the detailed examination ol the dynamical or 

 physiological aspect of plant life, it will be found of great 

 assistance if we devote a short time to the survey of the 

 special chemical elements which enter into the composi- 

 tion of the plant, and the conditions under which they occur 

 there. 



The easiest method of ascertaining the elements which 

 compose the food of plants is by subjecting the entire 

 plant to destructive analysis (footnote, page 25). The 

 plant organism contains a very large percentage of water 

 (uncombined) which can be dried off by application of a 

 gentle heat (desiccation). Many of the volatile oils and 

 aromatic substances are also got rid of by this means ; we 

 will not, however, consider them at present The amount 

 of the water present varies with the season of the year at 

 which the examination is conducted, and the plant and part 

 of the plant examine<J<^^dtib '^su^s, such as the Algse, 



