﻿292 Nash : Genus Syntherlsma in North America 



herbaria of the New York Botanical Garden, Columbia University, 

 and the Division of Agrostology at Washington, D. C., the latter 

 being kindly sent to me for this purpose by Professor Scribner, 

 to whom I desire to express my thanks for the courtesy. 



Descriptions of the genus and the species and their distribution 

 follow : 



SYNTHERISMA Walt. Fl. Car. 76. 1788. 



[D 



1772. Not Heist. 



Usually annual, sometimes perennial, commonly tufted grasses, 

 with simple or branched culms, flat leaves, and an inflorescence 

 composed of one-sided racemes which are variously arranged, 

 singly and alternate, in more or less approximate pairs, in whorls, 

 digitate, or in various combinations of these, the rachis 3 -angled, the 

 lateral angles often broadly winged, making the rachis appear flat. 

 Spikelets usually in pairs, sometimes in 3's or 4/s, from elliptic to 

 lanceolate, acute or acuminate, alternately arranged in two rows. 

 Scales 3 or 4, the outer 2 or 3 membranous ; first scale wanting 

 or minute ; second usually much larger than the first, rarely very 

 small, sometimes as long as the third ; third scale about as long as 

 the spikelet ; fourth scale chartaceous or indurated at maturity, 

 enclosing a palet of equal length and similar texture. 



The genus consists of some 25 or 30 species, widely distributed 

 in warm or tropical countries. Two or three of the species are 

 widely scattered as weeds, being almost cosmopolitan. 



Key to tlie Species. 



Rachis of the racemes with the angles naked, not winged ; first scale wanting ° r 



sometimes present as an inconspicuous rudiment. 



Second and third scales pubescent with appressed glandular 



tipped hairs ; culms simple or sparingly branched at 

 the base ; nodes 5 or less. 

 Racemes usually short, 2-10 cm. long ; spikelets less than 



2 mm. long. 



Racemes usually exceeding 10 cm. in length, rarely 

 shorter; spikelets 2.25 mm. or more long. 



Pubescence on the sheaths spreading ; racemes com- 



1. S. fdiformis. 



monly more than 5- 2. S. villosa. 



Pubescence on the sheaths appressed or nearly so ; 



racemes commonly less than 4. 3.5. leucocoma. 



Second and third scales glabrous. 



Hairs on the sheaths appressed or nearly so ; nodes 5 or 



less. 



