14 DISEASE IN PLANTS. 



mechanism, and its relations to the environment, 

 thus forms a subject apart from that which con- 

 cerns the chemical composition of the plant and 

 its environment, and this distinction designates, in 

 a word, as it were, the change which has been 

 brought about by modern biology. 



A point to be emphasised to the utmost where 

 agricultural students are concerned is that the 

 essential process of feeding is the same in a green 

 plant, a fungus, and an animal ; the greatest con- 

 fusion still exists with regard to this matter, owing 

 to misconceptions as to the real meaning of the 

 functions of the chlorophyll -corpuscles when 

 supplied with carbon-dioxide and water and the 

 energy of the sun's rays. The plant does not 

 feed on carbon-dioxide, any more than it feeds on 

 oxygen it feeds on the organic material after it 

 has been constructed, and the chlorophyll-function 

 is merely one mode of obtaining supplies of such 

 organic substance. 



Notes to Chapter II. 



In addition to the references in the last chapter, the 

 student should consult Sachs' Lectures^ XVII. -XIX., and 

 Pfeffer's Physiology, pp. 287-329, for the further development 

 of this subject. An excellent resume, with new facts and 

 points of view, will be found in Dr. Horace Brown's "Address 

 to the Chemical Section," British Association Reports, 

 Dover, 1899; and "Chemistry and Physiology of Foliage 

 Leaves" in Trans. Cheni. Soc, 1893, p. 604. See also Black- 

 man, " Experimental Researches on Vegetable Assimilation 

 and Respiration," Phil. Trans., 1895 ; and Parkin, "Forma- 

 tion, etc., of Carbohydrates in Monocotyledons," Phil. 

 Trans., 1899. 



