n6 PL A 'NT PHYSIOLOGY. 



acquire a knowledge of the leading facts, and clear ideas upon 

 the leading principles, of the main divisions of the subject. 



78. What are the essential facts and theories in the physiology 

 of Reproduction ? 



Answer very synoptically from a review of your knowledge 

 earlier acquired, and from your various other sources of infor- 

 mation. Following are important topics. 



(a) What is the fundamental relation of reproduction to 



growth ? 

 (//) What are the probable origin and phylogeny, and the 



physiological characteristics of asexual reproduction ? 



(c) What are the probable origin and phylogeny, and the 



physiological characteristics, especially the 4< advan- 

 tages,' of reproduction by fertilization ? 



(d) What is the origin and significance of cross-fertilization, 



and what mechanisms has it resulted in ? 

 (c) What is the nature of variation, heredity, rejuvenation; 



and what is the nature of the physiological connection 



between parent and offspring ? 

 00 What is the known physical basis of these processes 



(i.e., in cell-division, fertilization, etc.)? 

 (g) What is the relation of the ontogeny to the phylogeny 



of an organism ? 

 .(/i) What is the physiological significance of alternation of 



generations, parthenogenesis, xenia, results of graft- 

 ing ? 



Section 4. Irritability. 



It is a matter of every-day observation that plants, while 

 inheriting the general characteristics of their forms, have a 

 large power of accommodating the details of size, shape, 

 texture, etc., to the conditions of their immediate environment. 

 This power is termed Irritability. It is necessary now to 

 investigate the precise methods by which this accommodation 

 is brought about, and to become acquainted with its common 

 phases or manifestations. The important environmental in- 



