HITCHCOCK AND CHASE NORTH AMERICAN PANICUM. 



47 



wide, the main axis much exceeding the erect branches, the axes densely clothed with 



short pubescence having long, stiff hairs intermixed, the short-pediceled spikelets 



somewhat crowded; spikelets 5 to 6 mm. long, about 2 mm. wide, fusiform, pointed, 



short-attenuate at base, pilose; first 



glume clasping, more than half the 



length of the spikelet, acute, 3 to 5- 



nerved ; second glume and sterile lemma 



exceeding the fruit, 5-nerved, often 



obscurely reticulate; fruit 3.7 to 3.8 



mm. long, about 2 mm. wide, elliptic, 



apiculate. 



DISTRIBUTION. 



Fig. 29. — Distribution of P. texanum. 



Prairies and open ground, especially 

 on low land along streams, often a weed 

 in waste ground and cultivated fields, 

 Texas and northern Mexico. 



This is sparingly cultivated under the name of Colorado grass. 

 Texas: Dallas, Reverchon 1226 in Curtiss N. Amer. PL 3607A; Corsicana, Rever- 

 chon 2228; Pierce, Tracy 7748; Victoria, Plank 73; Austin, Plank 31; Har- 

 vester, Thurow in 1898; Wallisville, Wallis in 1880; Goliad County, Lea in 

 1874; San Antonio, Bush 1198, Havardin 1882; Corpus Christi, Hitchcock 163. 

 Mexico: Monterey, Hitchcock 5540. 



Dichotomiflora. — Annual plants with smooth culms, mostly large, spreading pani- 

 cles, the branchlets short and appressed along the ascending or rarely spread- 

 ing main branches; ligule membranaceous below, densely ciliate above, 1 to 

 3 mm. long; spikelets glabrous, narrow, acute or acuminate, 2 to 5 mm. long, 

 the first glume one-fifth to one-fourth as long, truncate or with a broadly trian- 

 gular tip; fruit smooth and shining. 



Panicles narrow, less than 1 cm. wide 16. P. vaseyanum. 



Panicles open, the branches usually ascending. 



Fruit acuminate; culms with a long, rooting base 19. P. elephantipes. 



Fruit not acuminate. 



Sheaths papillose-hispid 18. 



Sheaths glabrous 17. 



P. bartowense. 



P. dichotomiflorum. 



16. Panicum vaseyanum Scribn. 



Panicum vaseyanum Scribn.; Beal, Grasses N. Amer. 2 : 140. 1896. The only speci- 

 men cited is "Mexico, Pringle 1415." The type specimen, in the National Herba- 

 rium, was collected in the State of Chihuahua, in 

 "Wet places, pine plains, base of Sierra Madre, " Sep- 

 ' tember 30, 1887, by C. G. Pringle. 



DESCRIPTION. 



Plants spreading, branching at base and at the lower 

 and middle nodes, glabrous throughout; culms 50 to 

 70 cm. long, somewhat compressed; sheaths shorter 

 than the elongated internodes; ligules 1 to 2 mm. long; 

 blades 5 to 20 cm. long, 3 to 7 mm. wide, linear, scarcely 

 narrowed at the folded or enveloping base; panicles 

 terminal and from the axils of the upper leaves of the 

 main culms and large branches, narrow, 4 to 7 cm. long, less than 1 cm. wide, partially 

 included, equaled or exceeded by the erect uppermost blade; spikelets short-pediceled, 

 narrowly ovate, 2.5 mm. long, 1.1 to 1.2 mm. wide, subacute; first glume about one- 



FlG. 30. 



From type 



