GENERA OF GRASSES OF THE UNITED STATES. 215 



second glume and sterile lemma about as long as the fruit, 3 to 

 5 nerved, copiously silky; fertile lemma cartilaginous, lanceolate, 

 acuminate, usually brown, the flat white hyaline margins broad. 



Perennial grasses, the slender racemes erect or nearly so, aggregate 

 along the upper part of the main, axis, forming a white or brownish 

 woolly panicle. Species about 12, in the warmer parts of America 

 and in Australia ; 3 species in the southern United States. 



Type species: Andropogon insularia L. 



Valota Adans., Fam. PI. 2 : 495. 1763. The citation given by Adanson is to 

 " Sloan, t. 14. f. 2." which is also given by Linnaeus under his Andropogon in- 

 sularis, 1 which fixes this species as the type. 



Trichachne Nees, Agrost. Bras. 85. 1829. Nees describes five species, the first 

 of which, T. insularis, based on Andropogon insularis, is taken as the type. 



Valota is closely allied to Syntherisma, differing chiefly in the 

 acuminate fruit and the silky spikelets. 



Valota insuldrls (L.) Chase (Panicum lanatwm Rottb., P. leuco- 

 pJiaeum H. B. K.) (fig. 129), common in the American Tropics, with 

 brown or tawny inflorescence, is found in southern Florida. Valota 

 hitchcockii Chase, with short blades and short-pubescent spikelets is 

 a rare species from Texas and Mexico. Valota saccharata (Buckl.) 

 Chase (Panicum lachnanthum Torr.), with copiously long, silky 

 white spikelets, is common in the Southwestern States on rocky soil. 

 The first-mentioned species is not relished by cattle and in the West 

 Indies is called sour-grass. 'The third species is a constituent of the 

 ranges of the Southwest, but furnishes only fair forage. 



110. SYNTHEKISMA Walt., the crab-grasses. 

 (Digitaria Hall., not Heist.) 



Spikelets solitary or in twos or threes, subsessile or short-pedi- 

 celed, alternate in two rows on one side of a three-angled winged or 

 wingless rachis; spikelets lanceolate or elliptic, plano-convex; first 

 glume minute or wanting; second glume equaling the sterile lemma 

 or shorter ; fertile lemma cartilaginous, the hyaline margins pale. 



Annual or sometimes perennial, erect or prostrate grasses, the slen- 

 der racemes digitate or somewhat scattered, but aggregate along the 

 upper part of the culms. Species about 60, in the warmer parts of the 

 world; 12 species in the United States, mostly in the southeastern 

 part. 



Type species : Syntherisma praecox Walt. 



Digitaria Hall., Stirp. Helv. 2: 244, 1768, not Adans., 1763, nor Heist., 1759. 

 Haller describes two species. No specific names are used, but the first species is 

 associable by citation with . Panicum sanguinale L. (Syntherisma sanguinalis) 

 Mid the second with Panicum dactylon L. (Capriola dactylon}. The first is 

 chosen as the type. 



Syntherisma Walt., Fl. Carol. 76. 1788. Walter describes three species, 8. 

 praecox, S. serotina, and 8. villosa. The first of these is selected as the typo. 

 This is the same as 8, sanguinalis. 



1 Syst. Nat., ed. 10, 2: 1304. 1759. 



