THE DEHISCENCE OF ANTHERS BY APICAL PORES. 205 



sions as to the type of flower from which an apically de- 

 hiscent form of any of the classes here recognized may 

 have been derived, it seems that there is little relation 

 between the systematic affinities of a group and the 

 possibility of its containing apically dehiscent genera 

 or species. 



STRUCTURAL SIMILARITY OF MEMBERS OF THE SEVERAL 



TYPES. 



Structurally, the apically dehiscent forms may be assem- 

 bled into more or less natural and sharply limited cate- 

 gories. The Araceous type is a natural and sharply 

 limited one, distinguished by a uniformity of gross struc- 

 ture that renders unnecessary any summary of morpholog- 

 ical characteristics. The crowding of the anthers or their 

 fusion into a synandrium renders apical dehiscence the 

 most simple and the necessary mode, but the recognition 

 of this fact does not furnish an explanation of the changes 

 which have taken place in the development of the structure 

 now prevailing or indicate the forces which have been 

 active in producing them. Considerable is known of the 

 pollination of these forms but upon the basis of the data 

 which I have so far collected I am not yet prepared to 

 discuss the significance of insects as a factor in the 

 development of this floral type, or, to state the matter 

 differently, to say in how far apical dehiscence in this 

 type and the other structural characteristics correlated 

 with (or determining) it are to be regarded as adaptations 

 for fertilization by certain groups of animals. This 

 much is certain, that the members of the Araceous type 

 are distinct in every way from the others considered. 



This last statement also applies to the Gramineous type 

 which may also be dismissed from our further considera- 

 tion. 



The Polygalaceous type shows a great uniformity of 

 structure. The locules of the short, broad anthers open 



