Flora of North America species comparison

Except for its abundant and elongate trichomes, Atriplex argentea var. longitrichoma is a close match for the closely allied var. hillmanii. As in practically all other herbaceous Atriplex, the features of fruiting bracteoles are variable and transitional to those of other related taxa. The authors of A. longitrichoma indicated several differences between their new entity and A. hillmanii, e.g., size of fruiting bracteoles, “5–6 mm, 5–6 mm wide, vs. 3–4 mm, 3-4 mm wide.” Actual measurements of A. hillmanii bracteoles indicate a size range of 3.5–6.2 mm in length and 3.7–7.2 mm in width. Leaf blade measurements cited by Stutz et al. are “25–35 mm, 10–13 mm wide.” Leaf blades in the type series cited by those authors actually measure 8–40 mm and 5–18 mm wide. It is true that the shape of the leaf blade base is rather consistent in var. longitrichoma, tapering to a winged petiole or tapering to a sessile base. However, leaves with that identical shape are scattered throughout the range of var. hillmanii. The protolog of the taxon cites plant size as 10–20 cm tall, but the central stem in one of the isotypes is a full 30 cm tall.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In their extreme expression, the leaves of Atriplex argentea var. rydbergii are narrowly elliptic, tapering to both ends, but those extreme forms are connected through a graded series with oval-ovate ones, which tend to maintain the acute-cuneate base, however. The broad-leaved forms are intermediate to var. argentea. Tapering of leaf base to petiole is not restricted to this variety, however. Similar leaf shape occurs rather widely through the species as a whole, but in no place is it so consistently geographically correlated as in the Four Corners region.

H. C. Stutz and G. L. Chu (1997) compared their newly proposed Atriplex pachypoda from southwest Colorado and northwest New Mexico with the A. caput-medusae phase of what is considered herein as A. saccaria var. saccaria. Fruiting bracteole shape, marginal tooth arrangement, and compression are so strikingly similar to those of the A. argentea complex that the relationship with the latter group is apparent. Indeed, the closely contiguous var. rydbergii is nearly identical in all except subtle differences in bracteole shape and the disposition of staminate flowers in a terminal spike or panicle, which is apparently not an entirely constant feature. Arrangement of staminate flowers in terminal spikes appears at once to be a striking feature of var. rydbergii, but the spikes are evanescent, often lacking by fruiting time. And, there are some specimens of that variety in which the staminate flowers were evidently mainly, if not entirely, in axillary glomerules. Because of the similarities to var. rydbergii and the inconsistence of characteristics regarded by its authors as diagnostic, A. pachypoda is herein relegated to synonymy.

(Discussion copyrighted by Flora of North America; reprinted with permission.)