402 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



tions of the lemma between and outside of the awns; palet of lower floret pubescent 

 above, acuminate, that of the second floret with 2 short awns, both about 6 mm. long; 

 third floret a simple, undivided awn, a rudimentary lemma consisting of 3 long, pubes- 

 cent, scabrous awns, or a well-developed lemma resembling that of the second floret, 

 but smaller; caryopsis obovate, about 5 mm. long and 1.5 mm. wide, the scutellum 

 covering nearly the entire ventral surface, or only about one-half of it. (Plates 78, 

 79, 80, A.) 



This species occurs on familiar collecting ground where the most active botanical 

 collectors have worked for years and where the writer collected for about three years 

 before finding it. No specimens of it have been found in any of the herbaria exam- 

 ined. There are literally scores of acres where it forms one-half to three-fourths of 

 the entire vegetation and consequently is, locally, an important economic species. 



I first collected the species in the State of Sonora about a mile south of Nogales, 

 Arizona, and subsequently in several situations in northern Sonora and southern Ari- 

 zona. I have seen or collected it on the slopes of the Cananea Mountains, in the 

 Celero Mountains, where it is most abundant, and in the Santa Rita and Santa Catalina 

 Mountains. It is more likely to occur upon southern exposures, especially in the 

 Santa Rita and the Santa Catalina Mountains, where it may be neglected for the more 

 common and well-known Bouteloua chondrosioides. In some situations southeast of 

 Nogales, however, where it grows most luxuriantly, it might be mistaken for a hairy- 

 spiked form of B. curtipendula. This in itself indicates a striking variation in the 

 general aspect of the species. As indicated in the illustrations, the floral structure 

 is fully as variable. 



The type is Griffiths 7269, collected on southern exposures upon the northern slope 

 of the Santa Rita Mountains, Arizona, September 17, 1904. 



23. Bouteloua megapotamica (Spreng.) Kuntze. 



Pappophorum megapotamicum Spreng. Syst. Veg. 4 : Cur. Post. 34. 1827. The 

 type was collected by Sello "Rio Grande," Brazil. 



Eutriana multiseta Nees, Agrost. Bras. 413. 1829. This was described from a speci- 

 men in the Berlin Herbarium collected by Sello at Montevideo. This specimen 

 and a duplicate in the Trinius Herbarium have been examined. See also Kunth, 

 Rev. Gram. 2: 449. pi. 138. 1829. 



Pappophorum eutrianoides Trin.; Nees, Agrost. Bras. 414. 1829. Mentioned as a 

 synonym under Eutriana multiseta. 



Bouteloua multiseta Griseb. Abh. Ges. Wiss. Gottingen 16 : 303. 1879 (Symb. Fl. 

 Argent.). Based upon Eutriana multiseta Nees. 



Bouteloua megapotamica Kuntze, Rev. Gen. PI. 3 a : 341. 1893. Based upon Pappo- 

 phorum megapotamicum Spreng. 



DESCRIPTION. 



A cespitose, erect or ascending, strongly stoloniferous perennial; culms about 20 

 cm. high, erect or geniculate at base, not branched; sheaths close, striate, smooth; 

 blades rather rigid, abundant below, and often 10 cm. long, but short above, incon- 

 spicuously hairy especially on the lower surface, the edges hispid; ligule consisting of 



Explanation of Plate 78. — a, Spiko of Bouteloua eludens; b, spikelet; c, lemma of first floret; d, two 

 views of palet of same, one showing pistillate flower; e and/, lemma and palet with perfect flower of second 

 floret; g, rudimentary lemma of third floret; h, two views and cross section of caryopsis. a-f, Scale 5; g, 

 scale 7.5; h, scale 15. From type specimen. 



Explanation of Plate 79.— From type specimen of Bouteloua eludens and photograph taken in Santa 

 Catalina Mountains, Arizona. (5x7 No. 3076 Farm Management, U. S. Dept. Agr.) 



Explanation of Plate 80.— View showing the strong tufty character of Bouteloua eludens, on southern 

 exposures in Sabinio Canyon, Santa Catalina Mountains, Arizona, in the latter part of September. B . Bou- 

 teloua terana from the vicinity of San Antonio, Texas, where this grass is of minor importance, being usually 

 crowded by ranker species. Farther north, in the vicinity of San Angelo, it grows more nearly pure. 



