282 GENUS ATRIPLEX. 



the open, strict habit of the latter; the leaves are for the most part cordate at base, 

 always much broader in proportion to their length and hence more rounded-ovate; 

 the staminate glomerules are always in well-developed, open, naked, graceful terminal 

 panicles, instead of sessile in the upper axils, as they are in truncata. 



A reduction to A. argentea has been suggested, as noted under the minor variations. 

 But the differences here are even greater, for in addition to those just indicated as 

 separating saccaria from truncata, the normal fruiting bracts are very unlike in shape 

 and in the development of the free margins. However, there is a minor variation of 

 argentea (caput-medusae) in which the bracts develop remarkably large appendages 

 similar to those common in saccaria. Probably it was a comparison of plants in this 

 condition that led to the taxonomic reduction just mentioned. The unappendaged 

 bracts here furnish the dependable clue as to relationships, although the leaf and inflor- 

 escence characters also enable one to distinguish saccaria and argentea with certainty. 

 It should here be noted that the latter occasionally develops an elongated staminate 

 inflorescence. This, however, is rigid and spike-like, as compared with the slender, 

 curving panicle of saccaria. 



The original description of A. saccaria gives the bracts as "not at all appendaged." 

 This was due to an oversight, for, while most of the bracts on the type-sheet are not 

 appendaged, others, often in the same axils, bear a few appendages. 



ECOLOGY AND USES. 



Atriplex saccaria is the most typical indicator of bad-land shales. It is usually the 

 first and often the pioneer in rillways and on the many small fans in Bad Lands, and not 

 infrequently forms families on the crumbling slopes. The plants are typically low, com- 

 pactly branched, and closely aggregated, both habit and grouping significant of the extreme 

 xerophytic conditions and the precarious foothold. The salt-content usually ranges 

 from 1 to 2 per cent, but is often much higher. In more stable spots this species is 

 usually associated with A. dioeca or Eriogonum divaricatum. In ecological response it 

 is practically identical with A. graciliflora, due to the fact that both grow in the same type 

 of habitat. 



This plant has rarely been found to be grazed, probably because of its high salt-content. 



21. ATRIPLEX ARGENTEA NuttaU, Genera 1 : 198, 1818. Plates 43 and 44. Silverscale. 



Erect annual herb, 1.5 to 8 dm. high, freely branched from the base and globoid in 

 outline, or rarely with few branches and more strict; branches stout, angled, furfuraceous 

 when young, the whitish bark exfoliating in age; leaves alternate except the lowermost 

 ones, sessile or subsessile or the lower ones decidedly petiolate, lanceolate, ovate or deltoid, 

 2 to 5 cm. long (exclusive of petiole), 1 to 4 cm. wide (smaller in minor variation 1), 

 cuneate to subhastate at base (all narrowed to the base only in minor variation 9, A. 

 rydbergi Standley), mostly obtuse or only slightly acute at apex, entire or repand-dentate, 

 not exceptionally thickened, grayish-furfuraceous, glabrate; flowers monoecious, in 

 axillary glomerules and in terminal interrupted spikes, the staminate and pistillate 

 flowers usually mixing in the clusters, but the former mostly toward the ends of the 

 branches and sometimes forming purely staminate spikes; perianth of 4 to 5 sepals in 

 the staminate flowers, wanting in the pistillate; fruiting bracts sessile or subsessile, 

 more or less compressed, united to the middle or above, obovate or cuneate-orbicular, 

 4 to 8 mm. long, 4 to 10 mm. wide, including the green foliaceous margins, which are 

 subentire to variously laciniate, the faces smooth or appendaged or crested; seed 1.5 

 to 2 mm. long, brown; radicle superior. 



Abundant in moderately alkaline soils of western North America and northern Mexico; 

 southern Saskatchewan to western Texas, northern Chihuahua, California, and Idaho. 



