286 Flowers of Solatium rostratum and Cassia chamcecrista. [April, 



genera Androcera and Nycterium. The first has but one long 

 stamen, and S. rostratum may be taken as its type. This sub- 

 genus is confined to tropical America. Nycterium contains spe- 

 cies most of which have three long stamens, but some have only 

 one. A table of the species and their distribution is as follows : 



dubium I » « " Arabia and North Africa. 



Of the lateral asymmetry I cannot speak, for so far as I can 

 learn, it has not been noted. In the case of Cassia chama 'crista, 

 the unsymmetrical features are ( i) the curved style, (2) the oblique 

 stamens, (3) their abnormal number, and (4) the incurved petal. 

 The first is not peculiar, but is found in nearly all representatives 

 of the order Leguminosce. The second and fourth peculiarities 

 are such as are easily overlooked, and have not, so far as I find, 

 been noted of other species. The third peculiarity becomes, sig- 

 nificant when we compare this species with a typical one of the 

 genus, such as the one shown in the figure of C. q&itifolia, which 

 may also represent in general, Marylangica and occidentalis. Here 

 (Fig. 2) we usually have seven fertile stamens; in that (Fig. 3 <*) 

 we find the other three of the normal number ten, present, but 

 sterile, as if to indicate that some of the seven are derived from 

 the longer ones of the typical form. One or two of them in 

 cham<zcrista, instead of following the oblique position of the rest, 

 sometimes stretch out on the side of the pistil. 



The advantages of the arrangement in chamcecrista for securing 

 cross-fertilization over the more common form of the Cassicz, as 

 in acutifolia and occidentalis, I think may be seen withoutlurther 

 explanation. Moreover, if the insects visit the flowers for pollen, 

 we can readily see the advantage in having the stamens of un- 

 equal length, and hence the development by natural selection, of 

 the Androcera form of Solarium, and the typical Cassia from 

 among the Ccssalpinicce 



Before leaving the subjects suggested by these flowers, I 

 would indicate several points, and not having time to discuss 

 them more fully, we will leave them in the form of queries. 



I. These similar modifications occur in utterlydiver.se families, 

 having similar geographical distribution, viz : in tropical regions, 

 and perhaps the limitations may be further narrowed to the drier 



