STUDIES ON AMERICAN GRASSES. 



I. A REVISION OF THE NORTH AMERICAN SPECIES OF 



CAIAMAGROSTIS. 



By Thomas H. Kearney, Jr. 



INTRODUCTION. 



• In North America, north of Mexico, thirty-eight species of CaJama- 

 grostis are known to occur, eleven of which are here published for the 

 first time. All of these are native, no introduced species having as 

 yet been reported. All belong to the section Deyeuxia Hack. (Clarion, 

 as a genus), which is characterized by the usually hairy prolongation 

 of the rachilla behind the palea. This prolongation is villous along its 

 whole length to just below the apex,' except in C. cinnoides, which has 

 the extension of the rachilla naked to just below the apex, where it 

 bears a circle of long hairs, not unlike the pappus of some Cichoriacece, 

 C. cinnoides is also uuique among North American species in its pubes- 

 cent caryopsis. All of our species, excepting C. hreweri, have well- 

 developed creeping rootstocks and at least some of the innovations 

 extravagiual. The culms, usually simple, are sometimes branched in 

 C. langsdorffiiy C. canadensis, and C. macouniana. 



CLASSIFICATION. 



A satisfactory segregation of the North American species of Calama- 

 grostis is rendered difticult by their great variability and the existence 

 of a series of intergrading forms between many that are none tbe less 

 too distinct in the typical form to admit of their being united. Thus 

 from 6'. canadensis to C. langsdorffii a perfect gradation can be traced. 

 From C. liyperhorea to C. neglecta, on the one hand, and to C. inexpansa 

 on the other, the transition is equally uninterrupted. The consequent 

 impossibility of sharply defining some of tbe species has made it 

 expedient to regard several of these intermediate forms as varieties of 

 one of the two connected species, although rather arbitrary characters 

 must be used for distinguishing them. This frequency of intergrada- 

 tion has made the construction of a serviceable key a task of more 

 than ordinary difficulty. 



Quite naked abuorinally in ono or two species. 



