THE DEHISCENCE OF ANTHERS BY APICAL PORES. 237 



lia. I 



mi 



, At the present time, the importance of statistical methods 

 is being emphasized by many writers. In floral ecology, 

 attempts have long been made, and very successfully, too, 

 in many cases, to estimate exactly the relative importance 

 of each class of visitors in the evolution of a given flora. 

 The problem at present in hand differs essentially from 

 those which have preceded it in that it is an attempt to 

 separate certain floral types and estimate their relative 

 numerical importance in any flora. 



The difficulties encountered are very great and the result 

 obtained with the present material is not wholly complete. 

 The following is the method employed and the results it 



has yielded. 



The first requisite was the determination of the distri- 

 bution of the apically dehiscent forms. 



For the sake of convenience, the earth was divided into 

 fourteen regions. It hardly need be remarked that in the 

 present state of our knowledge any division into great and 

 sharply defined phytogeographic regions is purely artificial 



>relv as a convenience for further 





m 



study . 



Fourteen divisions were recognized, since, after 



careful consideration, it seemed best to adopt so far as 

 possible the floristic regions of Drude. 



It was deemed best to have the regions represent, so far 



as possible, systematic rather than ecological units. 



It 



my 



influence 



in the selection of the divisions to be used. The principal 

 need which led to the employment of a series of regions 

 was the desirability of making a statistical comparison of 

 the percentages of apically dehiscent genera belonging to 

 the various types in the several floras. To facilitate tabu- 



modified 



making 



or, in some 



cases, even political boundaries. "W 



: 



