172 



MISSOURI BOTANICAL GARDEN. 



It 





that the 



h h 



been 



done since the spring of 1904 has not materially modified 



has added more 



many 



In 



have 



not give a systematically arranged 

 considered. This, with the neces- 

 sary bibliographic citations and descriptive text and illus- 

 trations, would require far more space than is available. 



I shall rather divide the former 



nd 



describe these briefly, mentioning, when desirable, the 

 names of the genera assigned to the particular types, with 

 their geographical distribution, and comparing their struc- 

 ture briefly with the forms to which they are systemati- 

 cally related. It is to be i 

 types are not sharply de 



nderstood that these groups or 

 hied categories, but transgrcs- 



sive assemblages. The justification for the division of 

 the material into these groups or types is found in the fact 

 that the majority of the species do fall clearly into one or 

 the other of the groups, while those which represent transi- 

 tions or are quite aberrant in structure are much rarer. 

 These groups are to be regarded as tentative, and, while 

 for the most part natural, they are established primarily for 

 the convenience of the present discussion. Their great 

 justification is to be found in the convenience of treat- 



merit and interpretation which does result from their use. 



Four of these types I shall consider very briefly, merely 

 describing in general terms their differential characters. 

 The fifth, sixth and seventh will be treated in greater 

 detail, and in addition to the description and comparison of 

 the morphological features, I shall discuss their ecological 

 relations and geographical distribution. 



In this place I shall not review the work of others on the 

 microscopic structure of the apically dehiscent anther or 

 present the results of my own studies in this phase of the 

 problem. I wish here to confine my attention to a discus- 

 sion of the general morphological features and the e&ologi- 



