Holm, The genus Carex in North-West America. 
29 
As far as concerns the representation of the greges, \ve meet 
here with ^/ormae hehetatae^', „centrales^' and ,fdesciscentes^', thus 
several of the greges seem to be well developed within the region. 
Of these the interesting „formae liel)etatae‘% which evidently indicate 
the habit of ancestral types, these exhibit the same characters as 
observed in other regions viz. a lesser development of the inflores- 
cence besides the tendency to become dioecious. But otherwise 
they show invariably the same morphological structure of the 
perigynium, in no ways to be distinguished from that of the more 
evolute types, though readily recognized as that of a Yignea or 
of one of the Carices geniiinae. 
The study of the geographical distribution of a large genus, 
as for instance Carex. may throw some light upon the great problem 
as to the place of origin of certain species, and we believe that 
the abundance of a species and its association with allies must be of 
some weight in regard to this particular question: the geographical 
Center. A tabulation of all the flowering plants of the region, 
treated in the present paper, will no doubt show that North-West 
America constitutes a most important center as to distribution 
and development of a number of species, and perhaps the most 
important in North America. 
