FLORA OF THE DISTRICT OF COLUMBIA. 73 



1. Syntherisnia filiformis (L.) Nash. 



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

 ern states, north to Mass. {Panicum filiforvie L. ; Digitaria filiformis Koeler.) 

 The only native species in our region. 



2. S3?ntherisma 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 

 Pere.) 



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 sanguinale 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 2. 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 4. 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. miihlenbergii. 



1. Paspalum dissectum L. 



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

 Atlantic Coastal Plain. (P. mevibranaceum Walt.) 



2. Paspalum longipilum Nash. 



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

 Coastal Plain. 



3. Paspalum circulare Nash. 



Moist open ground and embankments, especially eastward. Aug. Conn, to N. C. 

 and Tex. 



4. Paspalum laeve Michx. 



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

 to N.J. 



The commoner form has blades pilose above, sometimes a^so toward the base beneath. 

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



