Some Generic Segregations 



BV P. A. RVDliERG 



(With Plates 13 and 14) 



The concept of a genus may vary among botanists as well as 

 among zoologists. To some a genus is an aggregate of all forms of 

 organisms which can be included within a certain artificial descrip- 

 tion or diagnosis ; to others it is a natural group of closely related 

 species or forms and may be modified, extended or limited as soon 

 as these forms become better known. It is unnecessary to state 

 that the former view nowadays has very few advocates, for nature 

 was never made to follow the narrow concepts of man. A system- 

 atist who holds the second view, tries first to find what species are 

 closely related, and when these are brought together, he tries to 

 draw a diagnosis of the genus. The limitation of a genus depends 

 naturally upon the personal views of the taxonomist. What is a 

 single genus to one botanist may to another constitute half a 

 dozen or more good genera, /. c, groups of related species. It 

 matters little how broad or narrow concepts we have of a genus, 

 if only we are consistent and in the same family or tribe desig- 

 nate as genera equivalent natural groups of related species ; /. c, not 

 making in one case the limits of a genus too large and in another 

 too narrow. 



I. An inconsistency of this kind exists, I think, in the usual 

 treatments of the family Mclanthaccae. Chrosperma and Stenan- 

 tJiium, Mclantliinni and Vcratruin, are separated by rather trifling 

 characters, while in Zygadcnus are included species of no closer 

 relationship. If we keep as distinct all of the first four genera, 



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