Holm, The genus Carex in North -West America. 29 



As far as concerns the representation of the greges, we meet 

 here with „formae hehetatae'' , „centrales" and „desciscentes" , thus 

 several of the greges seem to be well developed within the region. 

 Of these the interesting „formae hehetatae", which evidently indicate 

 the habit of ancestral types, these exhibit the same characters as 

 observed in other regions viz. a lesser development of the infiores- 

 cence besides the tendency to become dioecious. But otherwise 

 they shovv 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 Vignea or 

 of one of the Carices genuinae. 



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 fiowering 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. 



