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VoL. 30 No. 5 
BULLETIN 
TORREY BOTANICAL CLUB 
MAY, 1903 
Some Generic Segregations 
By P. A. RYDBERG 
(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, 7. ¢., 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 ; 7. ¢., 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 Melanthaceae. Chrosperma and Stenan- 
thium, Melanthium and Veratrum, are separated by rather trifling 
characters, while in Zygadenus are included species of no closer 
relationship. If we keep as distinct all of the first four genera, 
[The preceding number of the BULLETIN, Vol. 30, No. 4, for April, 1903 (30: 
197-270, fl. zz, 72), was issued 24 Ap 1903. ] 
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