THE DEHISCENCE OF ANTHERS BY APICAL PORES. 221 



clusively by pollen collecting bees, Melipona, Euglossa, 

 Augochlora, Megacilissa, E y hila and others. 



I have observed that 8. sisymbrifolium has a very pro- 

 nounced perfume, suggesting more abundant insect visits 

 than in many other species in which no fragrance is to be 

 detected. In the summer of 1903, 1 found large bees with 

 the greatest frequency collecting pollen. In his paper on 

 Brazilian solitary bees Schrottky gives 8. Balbisii (=8. 

 sisymbrifoliuni) as one of the principal flowers visited by 

 Xylocopa . 



Though few, these observations indicate clearly the true 

 method of pollination in the actinomorphic species of this 

 large genus. A few species are zygomorphic. Upon two 

 of these, direct observations have been made. Both have 

 been shown to be exclusively adapted to pollination by the 

 larger bees, Apis and Bombus having been observed as 

 well as some of the smaller Apidae. The numerous inter- 

 esting points incident to their zygomorphy and their ac- 

 companying lateral asymmetry cannot be detailed here. 



Between the zygomorphic Solanums and Cassias a most 

 remarkable ecological similarity prevails and it was this 

 which first called attention to the problem in hand. 



The floral ecology of the genus Cassia has attracted con- 

 siderable attention, the first suggestive observations being 

 those of Delpino and Leggett in 1871 to 1881. The paper 

 by Todd on Solatium rostvatum and Cassia chamaecrista 

 called particular attention to both of these genera and has 

 been the incentive to most of the later work. The more 

 important papers are those by Todd, Miiller, Burck, Harris 

 and Kuchs and the recent treatment in the third volume of 

 Knuth's Handbuch. • 



Since the appearance of Todd's paper and the more gen- 

 eral one by Miiller the attention of writers has been chiefly 

 devoted to the " division of labor " in the stamens and the 

 curious phenomenon of right- and left-handedness, or enan- 

 tiostyly as it has been called. 



