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THE DEHISCENCE OF ANTHERS BY APICAL PORES. 253 



Robertson and others have made valuable contributions to 

 this branch of statistical investigation. 



The scope of this paper does not include a general re- 

 view of the several attempts which have been made to 

 demonstrate a relationship between the geographical dis- 

 tribution of flowers and the insect environment. MacLeod 

 in the introduction to his careful investigation of the in- 

 sect relations of the flowers of the Pyrenees has given such 

 a review of the more important papers. Schimper and 

 Drude have doubtless performed a great service for this 



phase of biological investigation by recognizing animals ai 

 representing one of the factors in physiological plant 

 geography. 



In this paper I have sought to approach the problem 

 from a point of view different from that usually taken. 

 Previous researches have been almost exclusively exami- 

 nations of the range of individual species or genera 

 which are clearly adapted exclusively to a single polli- 

 nating agent, with the range of the organism to which they 

 are adapted, or statistical comparisons by the methods 

 of Miiller and MacLeod of floras of different regions, 

 lowland and alpine, insular and continental, temperate and 

 tropical and boreal. 



I have tried to select all floral forms of a given type and 

 after assuring myself of the reality of their morphological 

 semblance and, so far as our limited knowledge of the 

 plants in their living state would permit, of the similarity 

 of their ecological relationships, I have considered their 



geographical distribution throughout the main divisions of 



the <>Iobe. 



o 



This method as applied to the problem of the mor- 

 phology and biology of the apically dehiscent anther has 

 yielded results which are, I think, of some importance in 

 the larger problem of the evolution of floral structures. 



Any problem in geographical distribution is necessarily 

 dependent upon the validity of taxonomic or morphological 



A 



