404 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



ditions as is possible under field treatment, but plants of the same 

 line of descent growing side by side show such wide and fluctuating 

 differences in the degree of their self-fertility that there seems to 

 be no direct connection between these phenomena and the im- 

 mediate conditions of growth. Yet it is entirely possible that 

 the history of the varieties under cultivation and the spread of 

 the species in new regions may have been, in quite the Darwinian 

 sense, factors in inducing the physiological conditions that are 

 associated with the present existence of self- and cross-sterility 

 and fertility in the species. Careful and extended methods of 

 pedigreed culture are necessary to enable one even to guess at the 

 actual causes contributing to the development of such characters, 

 especially in view of the possibility that they are epigenetic and 

 intercellular in nature and manifest a wide range of fluctuating 

 variability. 



It is apparent, however, from the evidence accumulated since 

 Darwin's time that the phenomena of self-sterility as seen especi- 

 ally in such cases as EschsclioJtzia, Reseda, Cardamme, and Ci- 

 chorium are more than "incidental" as Darwin was inclined to 

 believe, and may have a special biological significance in explaining 

 the interrelations of living cells both in sex fusions and in vegeta- 

 tive growth, and the expression and heredity of such relations. 



The conception of sterility as developed by Baur, Correns, and 

 Compton, is manifestly too simple. They claim that such char- 

 acteristics as fertility and sterility can be stated in terms of rela- 

 tively fixed and constant units of germ plasm, and attempt to 

 analyze the internal conditions involved in incompatibility on the 

 hypothesis that these conditions are predetermined by the physi- 

 cal transmission of definite line stuffs as hereditary units which 

 are directly responsible for certain specific and individual difter- 

 ences on the one hand and similarities on the other. The evidence 

 in chicory is quite clear on this point. As described above, 

 crosses Ijetween self-sterile plants gave an Fi generation of 172 

 plants of which 15 showed some degree of self-fertility. The 

 study of the progeny of these self-fertile plants as to sterility and 

 fertility in self-fertilized line cultures gave results which are 

 perfectly clear and definite. Both the F2 and F3 generations show 

 that self-sterility and self-fertility are neither dominant nor 

 recessive characters in any consistent sense, thai the character of 



