

FLORA OF THE DISTRICT OF COLUMBIA. 73 



1. Syntherisma filiformis (L.) Nash. 



Common in open ground throughout our region, especially to the east. Sept. South- 

 ern states, north to Mass. (Panicumfiliforme L. ; Digitaria filiformis Koeler.) 

 The only native species in our region. 



2. Syntherisma ischaemum (Schreb.) Nash. 



A weed in lawns, gardens, and waste ground, less troublesome than S. sanguinalis. 

 Aug.-Oct. Eastern U. S. Native of Eur. (S. linearis Nash; Digitaria humifusa 



Pers.) 



3. Syntherisma sanguinalis (L.) Dulac. Crabgrass 

 A common and troublesome weed in lawns, and in cultivated and waste ground. 



July till frost. Throughout the U. S.; native of Eur. (Panicum sangumale L.; Digitaria 



sanguinalis Scop.) 



Plants in cultivated ground, with numerous branches rooting in all directions, sug- 

 gest a crab. 



8. PASPALUM L. 



Rachis broadly winged, partly infolding the spikelets; plants subaquatic. 



' * 1. P. dissectum. 



Rachis not winged ; plants terrestrial . 

 Spikelets 2.5 mm. long or more, borne singly in 2 rows. 



Sheaths and blades pilose *■ P. longipilum. 



Sheaths and blades glabrous or the sheaths ciliate only or the blades sparsely 



pilose. . .. . . 



Blades elongate, reaching the base of the panicle or overtopping it; spikelets 



suborbicular, 3-3.2 mm. long 3. P. circulare. 



Blades shorter, the panicle much exceeding them; spikelets not over 2.8 mm. 



long, broadly oval -_• •_ *• P - laeve> 



Spikelets not over 2 mm. long, borne in pairs, appearing as if in 3 or 4 rows. 

 Spikelets 1.6 mm. long or less; culms very slender. 

 Blades glabrous on both surfaces or pubescent above, linear-lanceolate. 



5. P. longepedunculatum. 



Blades densely pilose on both surfaces, linear 6. P. setaceum. 



Spikelets about 2 mm. long; culms less slender. 

 Sheaths and blades densely canescent or velvety; culms stiffly spreading. 



7. P. psammophilum. 



Sheaths ciliate only, the blades densely or sparsely pilose. 

 Blades linear, 3-5 mm. wide, commonly rather densely pilose. 



8. P. pubescens. 



Blades wider toward the middle, 6-10 mm. wide, usually sparsely pilose. 



9. P. muhlenbergii. 



1. Paspalum dissectum L. 



Found on the Potomac Flats in 1900; not since found in our region. Autumn. 

 Atlantic Coastal Plain. (P. membranaceum Walt.) 



2. Paspalum longipilum Nash. . 

 Moist open ground; Takoma Park, Glen Sligo, and eastward. Aug.-Oct. Atlantic 



Coastal Plain. 



3. Paspalum circulare Nash. „ p 

 Moist open ground and embankments, especially eastward. Aug. Conn, to in . «... 



and Tex. 



4. Paspalum laeve Micbx. 



Common in open ground and along roadsides. Aug.-Sept. Southern states, north 



to N. J. . ., 



The commoner form has blades pilose above, sometimes also toward the base beneatn. 



(P. australe Nash; P. laeve australe Hitchc.) 



