1886.] NATURAL SCIENCES OP PHILADELPHIA. 315 



than the supporters of the wider speculations seem to believe. 

 It is not the most eminent writers who assert that " cross-fertiliza- 

 tion is the general rule," "the greater number of flowers are 

 cross-fertilized," etc. (see Popular Science Review^ 18Y3), though 

 the casual expression of Dr. Asa Gray, in his papers of 1877, 

 that " many flowers freely self-fertilize," certainly might imply 

 self-fertilizers to be a minority of the whole ; but the same eminent 

 botanist has also said " it is a common case that flowers cross- 

 fertilize when duly served by insects or wind, and self- fertilize 

 when not," and this by no means bears the impression that he 

 regards self-fertilizing flowers as composing a particularly limited 

 class. Indeed no one is more severe than Dr. Gray on theory- 

 makers who run off in haste on one line of facts. The true 

 sentiments of Dr. Gray are that " cross-fertilization, we may well 

 believe, is a very risky affair," and in view thereof very few plants 

 have become wholly dependent on this mode, but act on the rule 

 to prefer cross-fertilization " if they can," but failing in this, to 

 self-fertilize, " if they must." And, though it is not so generally 

 understood, I think a careful study of Mr. Darwin's works will 

 show that this is essentially his view also. 



Though unwilling to concede that any material benefit comes 

 to the races of plants from the aid which insects give to plants 

 by cross-fertilization, the fact that some species are evidently 

 wholly dependent on this agency for fertility, is no less interest- 

 ing, and any original observations must have value to the student 

 of this branch of science. 



Cassia, in a general way, has been a subject of study. In 1875 

 Dr. Leggett writes (Bull. Torr, Club, p. 171) that Dr. Torrey had 

 noticed the difficulty Cassia niclitans had in rejecting its pollen. 

 Dr. Torrey believed, however, that though the anthers seemed to 

 provide a pore at the apex for the emission of pollen, they finally 

 slit longitudinallj'^, and thus permitted the pollen to escape. Dr. 

 Leggett does not seem satisfied of this. In 1882, however, Prof. 

 J. E. Todd published some extremely interesting observations on 

 this species, and on Solarium rostratum, which has a similar 

 staminal arrangement (see Am. Naturalist. Ap. 1882, p. 281-287). 

 C. Marilandica is referred to as one that would probably behave 

 in the same way. Before noting what Mr. Todd saw in these, I 

 will note the observations I have made on this species. 



As nothing seems to have been placed on record in relation to 



