44^> MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



existing between species ('69, \^. 436). The infertility even in self- 

 fertilization is here definitely considered as involving too great 

 a dissimilarity that is essentially a physiological differentiation. 



Jost's consideration of the cross-incompatibilities of intra-form 

 fertilization indicates that the doctrine of individual stufTs does 

 not adequately account for the results here obtained. He sug- 

 gests that different concentrations of the assumed individual stufT 

 may exist in organs of different length and from his discussion it 

 appears that illegitimate cross-pollinations which should be fertile 

 because in\ohing different stuffs are not fertile because of a 

 particular concentration. Thus certain degrees of concentration 

 of the individual stuff in sex organs of two different plants are 

 assumed to influence the degree of cross-fertility even to the 

 extent of prohibiting cross-fertilization. 



Darwin failed to see that the incompatibilities giving sterility in 

 non-dimorphic species such as Eschscholtzia californica and Reseda 

 odorata are undoubtedly of the same nature as those giving self- 

 sterility in plants of dimorphic and trimorphic species. This was 

 perhaps largely due to the fact that he did not know of cross- 

 incompatibility in such plants as Cardamine and Cichorinm, which 

 give group reactions with reference to interrelations quite as do 

 the dimorphic and trimorphic species. He further confuses the 

 whole subject in his culminating work on self- and cross-fertiliza- 

 tion by speaking of illegitimate pollinations of dimorphic forms as 

 similar to self-fertilization of a non-dimorphic species ('77, p. 343; 

 p. 351), largely on the conception that both were similar in respect 

 to effect on fertility. 



The evidence from the various species of dimorphic and tri- 

 morphic species clearly shows that morphological and functional 

 differentiation of various grades and degrees of intensity are in 

 evidence in and among plants of the same blood relationship; 

 that the two are not necessarily closely related ; that both are 

 subject to fluctuations and sporadic variations; and that the 

 incompatibilities giving stcrilil}- cxen in self-pollinations are to be 

 considered, as Darwin e\idently held, as resulting from too great a 

 related differentiation of the organs and cells involved in fertiliza- 

 tion. 



In the \ .irioiis dimorphic and trinioriihir species each form is 

 composed of indi\ iduaU w hosr tlowers are morphologicalh' differ- 



