300 GENUS ATRIPLEX. 



tate-leaved plant with the staminate glomerules much reduced, as will be seen from the 

 tracing presented here of the rare original plate (see fig. 40). The only variation suffi- 

 ciently distinct to justify particular mention is the one here described as subspecies 

 confinis (Standley). 



The western branch of A. pentandra constitutes the single subspecies muricata. This 

 has undergone a reduction in the size of the bracts and the reticulations of these are less 

 evident. But in all other characters its equivalent in the area of typica is frequently 

 encountered. Even the size of the bracts overlaps in the two subspecies, as is indicated 

 by the measurements given in table 26. It was through subspecies muricata, or some 

 similar form perhaps now extinct, that the 7 or more far-western species of the pentandra 



group were derived. 



ECOLOGY AND USES. 



Atriplex pentandra and its .subspecies are largely tropical and subtropical, and nothing 

 is known of their ecology or uses. 



26. ATRIPLEX ELEGANS (Moquin) Dietrich, Syn. PI. 5:537, 1852. Plate 46. 



Wheelscale. 



Erect or subdecumbent annual herb, 1 to 6 dm. high, branched from the base, the 

 branches usually erect or ascending but sometimes shortly spreading and the ends erect, 

 the whole plant rounded and bushy; branches slender or stout, more or less obtusely 

 angled, coarsely furf uraceous, glabrate and then stramineous, the bark persistent ; leaves 

 alternate except a few basal pairs, sessile or short-petioled, elliptic-spatulate, oblanceo- 

 late or oblong or in small plants sometimes elliptic or obovate, narrowed to the base, 

 obtuse or acute at apex, 0.5 to 2.5 cm. long, 0.2 to 0.7 cm. wide, entire or remotely and 

 acutely short-dentate, thin, white-furfuraceous on both sides or sparsely furfuraceous 

 and green above, only the midvein prominent; flowers monoecious, all in small axillary 

 clusters the lower of which are purely pistillate, the upper mixed or perhaps some near 

 the ends of the branches purely staminate; perianth of staminate flowers 4- or 5-cleft or 

 exceptionally 3-cleft, of pistillate flowers wanting; fruiting bracts short-pedicellate, 

 strongly compressed, united throughout (except the herbaceous margins), orbicular, 2 to 

 4 mm. in diameter, the margins acutely dentate all around, the terminal tooth sometimes 

 more prominent than the others, the faces either flat and unappendaged or with a single 

 low tubercle midway of the midvein or each face bearing 2 laciniate crests (only in minor 

 variation 2, variety thornberi Jones), scurfy when young, glabrate, only the midvein 

 prominent; seed 1 to 1.4 mm. long, pale to dark brown; radicle superior. (Obione ele- 

 gans Moquin, in DeCandolle, Prodr. 13-: 113, 1849.) Southwestern United States and 

 northern Mexico. 



SUBSPECIES. 



Atriplex elegans exhibits a natural divergence into two subspecies, each occupying its 

 own geographic area. In addition to these there is a form here listed as minor varia- 

 tion 2, which should perhaps be subspecifically treated. 



Key to the Subspecies of Atriplex elegans. 

 Fruiting bracts with broad deeply dentate margins; leaves pften dentate. Southern Arizona 



and eastward (a) typica (p. 300). 



Fruiting bracts with very narrow shallowly dentate margins; leaves entire. California and 



western Arizona (6) fasciculata (p. 301). 



26a. Atriplex elegans typica. — Plant usually 1.5 to 6 dm. high; leaves elongated, 

 1 to 2.5 cm. long, entire to saliently denticulate; fruiting bracts with a broad herbaceous 

 border which is sharply toothed or laciniate, the teeth 1 mm. long when well developed. 

 {Obione elegans Moquin in De CandoUe, Prodr. 13^: 113, 1849.) Western Texas to south- 

 ern Arizona, eastern border of California, Sonora, and Chihuahua. Type locality, 

 Sonora. Collections: El Paso, Texas, Jones 4171 (Gr, US) ; Mesilla Valley, New Mexico, 



I 



