192 Trans. Acad. Sci. of St. Louis. 



polygamous. The large percentage of sterile flowers, caused 

 by cessation of development of the pistil, might indicate that 

 the failure of the pistil of the more terminal flowers to 

 develop is due to defective nutrition. It seems highly prob- 

 able that the condition is not a pollination adaptation, that is 

 one evolved primarily to secure a division of labor in the 

 flowers. The flowers of both species are rather conspicuous, 

 those of S. sisymhri folium especially so, without nectar, as 

 is characteristic of the genus, and without odor in 8. Caro- 

 linense but with a very pronounced odor closely resembling 

 that of 8. rostratum in 8. sisymhrifolium . The only pub- 

 lished observations on the pollination of >S'. Cai^oUnense of 

 which I am aware are those of Robertson* who describes the 

 flowers as adapted to Humble Bee females which visit them 

 for pollen. He saw B. Americanorum F. collecting pollen. 

 The flowers of this species are very rarely visited by insects. 

 During the three summers I have been particularly interested 

 in Solanum pollination I have only once seen Bombus col- 

 lecting pollen but much of the time my opportunities for 

 field work were not the best. My sister informs me that at 

 Lawrence, Kansas, during the summer of 1903 the flowers 

 were not much visited but that especially in the early morning 

 one could usually find at least one Humble Bee working on the 

 flowers." The very noticeable perfume of 8. sisymhrifolium 

 suggests more frequent insect visits. During the summer of 

 1902 when only one bed of this species was grown at the 

 Garden no insect visits were observed, though fruit was borne 

 freely, but in 1903 when the collection was much more ex- 

 tensive large bees were observed collecting pollen with the 

 greatest frequency. In his paper on Brazilian Solitary Bees 

 Schrottky givesf 8. Balbisii Dun (^ = 8. sisymbinfolium) , 

 as one of the principal flowers visited by Xylocopa. 



It is certainly of interest to note that in at least one 

 species of the genus, 8. Amazoniuni, the pistil is not the 

 only organ markedly affected. The species was first described 



* Robertson, C. Flowers and Insects. This journal 5 : 582. 1892. 

 t Schrottky, C. Eiisaio sobre as Abelhas Solitarlas do Brazil. (Revista do 

 Museu Paulista. 5:458). 1902. 



