208 MISSOURI BOTANICAL GARDEN* 







tions of the globe had been cast in the same mould or 

 formed by the same skilled artisan — is so exact and the 

 general structural habit of the aberrant forms is with all of 



the minor differences so uniform in essentials that it seems 

 necessary to attribute it to some single factor or co-opera- 

 tive group of factors of environment. 



Before we attempt to determine this factor, however, it 

 will be well to assure ourselves as fully as possible of the 

 real existence of such a structural uniformity. 



Of the structural characteristics, our knowledge is fairly 

 satisfactory, although many points can be determined only 

 by the examinations of living material. The large series 



of icones, many of them executed from living material, 

 in the library to which I have had access while carrying on 

 this work has enabled me to make extensive comparisons 

 otherwise impossible. It may, I think, be demonstrated 

 beyond confutation, that the apically dehiscent forms 

 other than the genera which have been assigned to groups 

 designated as the Araceous, Gramineous, Polygalaceous 

 and Ericaceous types (and all of which are, with the ex- 

 ception of the last, perfectly natural and sharply defined 

 categories) may also be grouped in classes few in number 

 and uniform in their essentials of structure. 



The close structural agreement among themselves of the 

 apically dehiscent forms assigned to any class is relatively 

 easy of demonstration or refutation although specific varia- 

 bility in many genera, the presence of minor structural 

 characteristics which tend to obscure the more essential 

 features, and the inadequacy of our knowledge of many 

 forms, renders this no light task. 



The demonstration of a general structural similarity in 

 all the parts of flowers, which have been brought together 

 for comparison on the basis of a single characteristic — in 

 the present case the mode of dehiscence of the anther — 

 indicates that there exists a correlation between this 

 character and the other structures of the same flower. 



