234 



MISSOURI BOTANICAL GARDEN. 



produce fruit when left to themselves, but produce seed 

 abundantly when artificially self fertilized. 



Little is known of forms outside the type family. Ducke 

 observed Centris and Xylocopa visiting the magnificent 



( 



) 



insigne but nothing is recorded concerning the objects of 



the visits. 



RECAPITULATION. 



s 



immarzing this section, we may say that our knowl- 

 edge of the ecology of these forms is far from satisfactory. 

 Our acquaintance with the ecological relations of the Dil- 

 leniaceous type justify no conclusions, but for the Solanum- 

 Cassia and the Melastomataceous types nearly all the 

 direct observations which we have and the entire mass of 

 comparative data indicate adaptation to the Apidae and 

 among these, for the most part, to those which are active 

 in the collection of pollen. The absence of nectar prac- 

 tically limits the range of visitors to pollen-feeding flics 



At 



The evidence for adaptation 



to the latter is very great. As to the origin or method of 

 evolution of these types of a< 



our evidence will 



not 



but 



h 



ty 



their 



We 



must now leave this phase of the subject which I 

 hope to take up briefly again after considering the data 

 of two other sides of the problem. 



The Geographical Distribution of Apically Dehiscent 



Forms. 



In the introduction to this paper, it was suggested that 

 the flora of certain regions is richer in apically dehiscent 

 forms than is that of others. The examination of this 

 hypothesis was one of the principal objects of the investi- 

 gations described. 



The Solanum-Cassia type seems to be the one best adapted 

 for a first study of this question. 



