41 6 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



made between plants A and C and plants of the E series were 

 fertile, but not all wide crosses are successful, as the use of pollen 

 from plant A on various plants of the variety red-leaved Treviso 

 shows. Also it should be noted that the cross-fertility of closely 

 related plants as /I and C (table 2),^ a.ndAQ,A and A2'/ (table 9) 

 may be quite as great as that between two more widely unrelated 

 plants as A and E22. The data for crosses within lines of known 

 descent given in tables 11-14 seem to indicate that there are a 

 large number of failures compared with those of crosses between 

 widely unrelated stocks. Individual cases of high fertility occur 

 quite the same in both, all of which emphasize the wide variations 

 of the processes involved in incompatibility. 



The occurrence of cross-sterility and cross-fertility between 

 plants of different races or strains of chicory supports the view 

 that such plants develop similar conditions in this respect in- 

 dependently of their possession of the germ cell elements that may 

 be present. These facts emphasize that the conditions deter- 

 mining self-sterility or cross-fertility are in a high degree individual 

 rather than purely related to racial differences, and suggest that 

 the type of cell organization in any particular organ ( the style) 

 may be highly individual and relatively duplicated in widely 

 different races on the hypothesis of zygotaxis. These considera- 

 tions make it evident that the role of the particular content of 

 the idioplasm in respect to the development of compatibilities 

 and incompatibilities in fertilization is secondary to this more 

 general cell organization that is affected by differentiation of sex 

 organs. 



Relation of vegetative vigor and fertility to inbreeding and cross- 

 breeding. — Closely associated with the foregoing topic is the 

 question of the influence of inbreeding and cross-breeding on 

 vegetative vigor and on the degree of fertility or sterility (of all 

 sorts) . 



Darwin sought to establish the law that "nature abhors self- 

 fertilization" and that cross-fertilization increases vigor and 

 fertility while self-fertilization decreases vigor and fertility. 

 This Darwin assumed to result because of increased dissimilarity 

 through crossing as contrasted with decreased dissimilarity through 

 selfing of sexual elements respectively. Darwin approached the 

 whole question of cross- and self-fertilization from the standpoint of 



