B.P.I. -42. G.F.P.I.- 



NORTH AMERICAN SPECIES OP LEPTOCHLOA. 



INTRODUCTION. 



In presenting the following review of the genns Leptochloa I have 

 been able to bring together our knowledge of this group of grasses 

 without describing any new species. In regard to the latter, botanists 

 will probably be thankful. But, on the other hand, I have been con- 

 strained in several cases to unite species kept separate by others. 

 All will not agree with me in the course I have taken in this respect. 

 It is always difficult to decide where specific lines shall be drawn, but 

 I have been governed by this rule: When two or more forms are con- 

 nected by numerous intergrading specimens they are to be considered 

 as the same species, although typical specimens of the extreme forms 

 may be easily distinguished. 



The notes are based mainly upon the Herbarium of the U. S. 

 Department of Agriculture, but through the kindness of those in 

 charge I have had the opportunity to examine the collections at the 

 Missouri Botanical Garden, the Gray Herbarium, the New York 

 Botanical Garden, and the Philadelphia Academy of Natural Science. 

 I have also examined the specimens in the larger European herbaria, 

 to the directors of which I wish to express my thanks for the privilege. 



For the purpose of this paper it seemed not worth while to enumer- 

 ate all the specimens examined, but a number of representative 

 specimens from numbered sets have been indicated for easier refer- 

 ence. 



KEY TO SPECIES OF THE UNITED STATES 



1. Spikelets usually short-pediceled (sessile in L. spicata, but flowers several), 

 arranged somewhat distantly along the branches of the panicle, not so con- 

 spicuously one-sided as in the following group; 4 to several flowered (2-flow- 

 ered in some forms of L. dubia) . 2 



1. Spikelets nearly sessile in two or more rows on one side of the branches of the 



panicle, 2 to 4 flowered and usually closely imbricated (more distant in 

 L. mucronata) 7 



2. Panicle simple or often reduced to a single branch or spike spicata. 



2. Panicle compound ' 3 



3. Spikelets 4 (2) to 6 flowered . 4 



3. Spikelets many flowered, elongated 6 



