362 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



The above characterization is drawn from the short-awned form which corresponds 

 with the type. 



This species is variable. Hitchcock's no. 6776 from Balsas, Mexico, is very differ 

 ent in color, especially from the northern Sonora plants. 



In 1904 between Imuris and Santa Ana in the State of Sonora I collected under no. 

 6834 two more or less distinct forms. One, which grew in a favorable depression, is 

 tall and rank, with abundant leafage, and is short-awned. The other, which grew 

 on a contiguous gravelly knoll, shows both short and long-awned forms, but on sepa- 

 rate plants. 



Collections have commonly included both forms under the same number. But one 

 thing is peculiar — the two forms are seldom found on the same plant. Both forms 

 produce seed and in exactly the same relative position. Pringle's no. 4559 contains 

 both forms, but the long-awned one has the spikes greatly reduced, the two lower 

 spikelets being very much aborted. Palmer's nos. 1261 of 1891 and 705 of 1890 show 

 both forms also. Not until Hitchcock's 1910 collections from Mexico came in were the 

 two forms found on the same plant. This does not appear to be a case of lengthening 

 of the awns after anthesis, as with Bouteloua chondrosioides, but a true dimorphic 

 character. The species is distributed from the Rio Grande region of western Texas 

 to Arizona and southward to the state of Colima. 



Palmer's no. 345 of 1887 from Guaymas, Mexico, has a habit, which is unique. The 

 culms instead of being geniculate-stoloniferous are erect-proliferous with the same 

 knotty appearance at the nodes, but perfectly erect and not rooting. 



HERBARIUM SPECIMENS. 



Texas: Havard 30, and 2, El Paso to Presidio. Nealley, Chenata. 



Mexico: Palmer 18, Yaqui River, Sonora; 345, 161, Guaymas; 66, Chihuahua; 270, 

 Guadalajara; 126, 112, Colima; 705, Alamos; 1460, 1459, Ymala. Pringle 597, 

 Altar; 4559, Tequila. Hitchcock 3528, Llano. Brandegee 1, 2, Culiacan. 



4. Cathestecum stoloniferum (Fourn.). 



\Atheropogon stolonifer Fourn. Mex. PI. 2 : 140. 1881. The type is Liebmann 



"La Parada, Sierra de Oajaca." As this specimen has not been examined, the 



scription and cited locality are our only guide. The name is appropriate and the 



:ription fits the plants referred here. Founder's characterization of spike details, 



jver, is not so satisfactory. „ t . 



A low, creeping, stoloniferous perennial, 10 to 15 cm. high, forming at times a 

 moderate turf; culms erect or geniculate, 10 to 15 cm. high, with stolons rooting readily 

 and bearing small tufts of leaves at intervals of 8 to 10 cm.; sheaths short, striate, 

 smooth, the nodes smooth except when geniculate and then hairy, the ligule con- 

 sisting of a few, long, white hairs; spikes 4 to 6, triangular in general outline and 

 about 13 mm. long; first floret pistillate, the second staminate, with or without one 

 or two rudimentary additional ones, the latter always more numerous and better 

 developed in the upper central spikelet; glumes of lower spikelets densely hairy, 

 narrow, keeled, acuminate, short-awned, the lower more than 2 mm., the upper 

 more than 4 mm. long, the lower glume of the upper spikelet reduced to a nerveless 

 fan-shaped, fimbriate scale scarcely 1 mm. long; lemma of the lower floret coriaceous, 

 pubescent, about 6 mm. long including the awns; central awn about 2 mm. longer 

 than the lateral; lateral awns of the lower spikelets often unequal in the second floret, 



