A. WRIGHTI — A. BRACTEOSA. 305 



acute at apex, 2 to 7 cm. long, 0.5 to 2.5 cm. wide, coarsely sinuate-dentate or repand- 

 dentate or many of the leaves entire, thin, sparsely scurfy but soon glabrate and green 

 on the upper surface, permanently white-scurfy beneath, strongly 1 -nerved; flowers 

 monoecious, the staminate glomerules in naked terminal panicles 5 to 30 cm. long, the 

 pistillate flowers in nearly all of the leaf -axils; perianth 5-cleft in the staminate flowers, 

 wanting in the pistillate; fruiting bracts short-stalked or sessile, well compressed, united 

 to about the middle, euneate-orbicular, 2 to 3 mm. long, 2.5 to 4 mm. broad, the con- 

 spicuous margins greenish above the middle and acutely gash-toothed, the faces usually 

 not appendaged, but with 3 nerves from the base; seed 1.2 to 1.5 mm. long, brown; 

 radicle superior. 



Southwestern New Mexico, Arizona, and northern Sonora. Type locality. New Mex- 

 ico. Collections: Type collection, Wright 1743 (Gr, NY) ; Mangas Springs, Grant County, 

 New Mexico, Metcalfe 639 (NY, US) ; Grain's Ranch, northwestern Grant County, New 

 Mexico, July 18, 1900, Wooton (US); Old Camp Goodwin, Arizona, Rothrock 343 (US); 

 Clifton, Arizona, Davidson 2937 (US) ; Williams, Arizona, Griffiths 4924 (US) ; cultivated 

 lands at Tempe, Arizona, Kearney 96 (US) ; Santa Cruz Valley, Tucson, Arizona, Thorn- 

 ier 134 (UC) ; Catalpa, Arizona, MacDougal 749 (US). 



SYNONYM. 



1. Atriplex radiata Coulter, Contr. U. S. Nat. Herb. 2:368, 1894.— Intended by Coulter to replace the 

 name A. wrighti, because of the earlier Obione elegans radiata Torrey. But Torrey's name, in addition to 

 having only varietal rank, is not now desirable, since it covered plants of A. elegans as well as of ^. tvTighii, 

 and, moreover, its descriptive features are misleading for the present species. 



RELATIONSHIPS. 



Atriplex wrighti stands between A. pentandra muricata and A. bracteosa, both geograph- 

 ically and phylogenetically. Its origin from the former or from some slightly more prim- 

 itive ancestral stock seems reasonably certain. It has a closely similar habit. The 

 fruiting bracts are slightly reduced in size but retain the characteristic reticulate vena- 

 tion. The leaves have modified their shape and become for the most part broadest 

 above the middle. This is looked upon as a later development from the usual lanceolate 

 or ovate shape. On the other hand, the inflorescence exhibits no reduction, the elongated 

 staminate panicles being especially well developed. Since the inflorescences usually are 

 much reduced in muricata, it is probable that wrighti diverged from the common stock 

 before the present characters of the former were firmly fixed. The connection with 

 bracteosa will be discussed when this species is reached. 



ECOLOGY AND USES. 



Atriplex wrighti forms dense consocies in river valleys with somewhat alkaline soil, 

 often making pure stands 3 to 4 feet in height and almost impenetrable, but usually asso- 

 ciated with Amarantus palmeri and Eriochloa polystachya, and less commonly with Kal- 

 stroemia grandiflora. It grows sparsely along roadsides on the mesas, but becomes a weed 

 in valley roads and in cultivated fields. 



The vigorous growth and palatability of this species render it of considerable value for 

 grazing, as indicated by the fact that it is grazed close to the ground in dry seasons. It 

 gives promise of becoming a valuable forage plant under cultivation. 



29. ATRIPLEX BRACTEOSA (Durand and Hilgard) Watson, Proc. Am. Acad. 9:115, 1874. 

 Plate 47. Bractscale. 



Erect or decumbent annual herb, 3 to 10 dm. high, the stems commonly spreading to 

 form dense tangled mats 5 to 30 dm. across, from which arise slender erect or ascending 

 twigs, or whole plant erect, slender, and sparsely branched in some forms (see minor 

 variation 4) ; branches thick, obtusely angled or grooved, sparsely scurfy, soon glabrate 



