2i8 PLANT PHYSIOLOGY 



(g) The hereditary ground form, and deviations therefrom in tor- 

 sions, fasciations, etc., and extent to which it is modifiable 

 by experiment. (On this subject Goebel's new "Einleitung 

 in die Experimented Morphologie," Leipzig, Teubner, 1908, 

 will no doubt rank as the standard work.) 



Literature of Growth. The subject is thoroughly summarized 

 by Pfeffer and by Jost, and there are no papers of more recent date, 

 aside from those cited, so far as I have found. 



10. REPRODUCTION. 



Very closely bound up with Growth, in the lower plants 

 coincident with it, and in the higher simply a special phase 

 of it, is that other form of Increase called Reproduction. Its 

 physiological phenomena are vastly important, but they do not 

 admit of profitable experimental study in such a course as 

 this. Some of them are bound up with cytology, others are so 

 recondite as to be open only to very refined investigation, while 

 others belong rather to that special phase of physiology called 

 ecology. Accordingly the student may most profitably work 

 up the subject through the accessible literature, concentrating 

 Ms attention upon the following matters: 



(a) The fundamental (or philosophical) relation of Reproduction 



to Growth, involving the physiological relations of parent 

 to offspring. 



(b) The physical basis of reproduction in cell, nucleus, and chromo- 



some, both as to divisions and fusions. 



(c) The relation of the ontogeny to the phylogeny of an individual. 



(d) Thq physiological characteristics, with the probable origin and 



phylogeny of asexual and of sexual reproduction, this involv- 

 ing the advantages of fertilization and the meaning of sex. 



(e) The mechanical and physiological evolution of fertilization 



mechanisms, and the limits of sexuality in the higher plants. 



(/) The probable advantages of cross, contrasted with close, fer- 

 tilization, and the mechanisms it has developed. 



(g) The nature and significance of variation, rejuvenation, and 

 senescence. 



(h) The significance of the special features, parthenogenesis, xenia, 

 double fertilization, independence of grafted parts, alterna- 

 tion of generations. 



