Atriplex argentea var. longitrichoma

(Stutz

Rhodora 102: 421. 2001.

Common names: Pahrump orach
Endemic
Basionym: Atriplex longitrichoma Stutz G. L. Chu & S. C. Sanderson, Madroño 45: 128, figs. 1, 2(left), 3. 1998
Treatment appears in FNA Volume 4. Treatment on page 351. Mentioned on page 350, 352.

Stems densely branched, mostly forming low broad clumps, 0.9–3 dm; branches terete, spreading or ascending, proximal ones to 30 cm, obscured by clavate unicellular trichomes. Leaves sessile or some petiolate; blade elliptic to ovate, oval, or lanceolate, 8–35 × 5–18 mm, base narrowly cuneate, margin entire, grayish scurfy. Flowers in mixed axillary glomerules. Fruiting bracteoles substipitate, ovate to obovate or suborbicular in profile, 5–6 × 5–6 mm, compressed or some thickened, margin deeply and acutely dentate, faces naked or covered with few to numerous appendages. 2n = 36.


Phenology: Flowering summer–fall.
Habitat: Saline valley bottoms, with shrubby saltbush, creosote bush, mesquite, and annual weedy grasses and forbs
Elevation: elevation not known

Discussion

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.

Selected References

None.

Lower Taxa

None.
Stanley L. Welsh +
(Stutz +
Atriplex longitrichoma +
Pahrump orach +
Calif. +  and Nev. +
elevation not known +
Saline valley bottoms, with shrubby saltbush, creosote bush, mesquite, and annual weedy grasses and forbs +
Flowering summer–fall. +
Obione argentea +
Atriplex argentea var. longitrichoma +
Atriplex argentea +
variety +