340 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



tions. Two plants grown from such seed were feebly or semi-self- 

 fertile ; the next year plants (number not given) raised from this self- 

 fertilized seed were likewise feebly self-fertile. The experiments 

 are not extensive nor are pedigrees indicated, yet it is clear that 

 some plants were fully self-sterile and others self-fertile to some 

 degree, giving different results in Brazil, England, and Germany, 

 which Darwin concludes is evidence of an influence of climate 

 acting on the sexual constitution ('77, p. 333)- 



With Abutilon Darwinii there was a feeble self-fertility in at 

 least some of the plants grown in England from the cross-fertilized 

 seed of plants which Miiller found to be self-sterile in Brazil. 



Three plants belonging to two varieties of Senecio cruentus were 

 completely self-sterile, but fully cross-fertile. 



Darwin describes his experiments with Reseda odorata in con- 

 siderable detail. Seven plants grown in 1868 were fully self- 

 sterile in all controlled pollinations which were made, although 

 three of them produced seed by spontaneous pollination which, as 

 Darwin points out, may have been accidental cross-pollination. 

 Sixteen combinations of cross-pollination involving five of these 

 plants were, it appears, fertile. The next year, however, three 

 plants raised from a new supply of seed were strongly self-fertile 

 and one other plant was feebly self- fertile. In 1870 six more 

 plants were grown; two were almost completely self-sterile and 

 four were strongly self- fertile. In 1871, of five plants grown from 

 seed of the self-fertile plants of 1870, three appeared to be feebly 

 self-fertile. No evidence of cross-sterility was found in any of 

 these plants. 



In Reseda lutea, Darwin observed self-sterile plants and isolated 

 two for study, one of which was "quite self-fertile," w^hile the other 

 was "partially self-sterile." 



{h) Regarding the nature and causes of self-sterility due to 

 physiological incompatibility, Darwin points out that this sort of 

 self-sterility is widely distributed, that it differs much in degree in 

 different plants, and that among individuals of the same parentage 

 some may be self-sterile while others are self-fertile, quite as re- 

 vealed by the pedigreed cultures of Cichorium which I shall report 

 later and which, no doubt, would likewise ajjpear in Cardamine and 

 in Nicotiana hybrids were attention especially given to this point. 

 The phenomenon appeared, as he observed it, in plants of cross- 



