14 



WESTERN ALLIES OF CAREX PENNSYLVANICA 



By Kenneth K. Mackenzie 



While typical Car ex pennsylvanica Lam. is found in the wooded 

 regions west of the Mississippi River as far as North Dakota, 

 it is essentially an eastern species. The plant of the western 

 prairies, plains and foothills heretofore referred to that species 

 is well marked, and distinguished from the eastern plant by a 

 number of characters. In addition, two plants of the Pacific 

 coast, geographically widely separated, have heretofore been 

 distinguished, but as they have rarely been collected, the points 

 of difference between them and the more eastern species have 

 never been fully gone into. 



One taking up the group soon notices that all three of the 

 western plants differ constantly from the eastern species in 

 the larger perigynia. Those of the western species average fully 

 2 mm. in width, while those of the eastern species are about 1.5 

 mm. The western species, too, have the sides so convex that 

 the body of the perigynia appears globose. In the eastern species 

 the sides are so much less convex that the body of the perigynia 

 appears globose-triangular. 



The heretofore unnamed species, described below and one 

 of the far western species {Carex verecunda Holm) also differ 

 from Carex pennsylvanica Lam. and the other far western species 

 {Carex vespertina (Bailey) Howell) in having the beak of the 

 perigynia strongly whitish tipped and deeply bidentate. The 

 two last-named species have the beak of the perigynia but little 

 whitish tipped and only shallowly bidentate. The newly 

 described species also has short stiff culms as compared with the 

 taller, and more slender culms of Carex pennsylvanica. Other 

 points of difference between the four species are shown in the 

 following key and description : 



Mature perigynia 2 mm. wide or more, the body round in cross section 

 Beak of perigynium deeply bidentate, strongly whitish tipped 



Pistillate spikes subglobose, sessile C. heliophila. 



Lower pistillate spike oblong, peduncled C. verecunda. 



