Euphorbia polycarpa |
Euphorbia aaron-rossii |
|
---|---|---|
smallseed sandmat |
Marble Canyon spurge, Ross' or Marble Canyon spurge |
|
Habit | Herbs, perennial, with deep stout rootstock. | |
Stems | erect, branched, densely clumped, previous year’s dead stems persistent, 25–45(–60) cm, glabrous, striate. |
|
Leaves | alternate, persisting, usually reflexed, occasionally spreading; stipules 0.1–0.3 mm; petiole 0.2–2.2 mm, glabrous; blade narrowly ovate to lanceolate proximally, narrowly lanceolate, linear, or filiform distally, 10–32 × 0.5–6.5 mm, base cuneate, margins entire, apex acute, surfaces pilose when young, sparsely strigose or glabrous with age; venation obscure, only midvein conspicuous. |
|
Involucre | turbinate to campanulate, 2.2–3.7 × 1.5–2.5 mm, moderately strigose; glands 5, dark green, reniform, 0.7–1.1 × 1–1.6 mm; appendages white to pink, flabellate, 0.5–1.5 × 0.8–2.2 mm, dentate or erose. |
|
Staminate flowers | 20–25. |
|
Pistillate flowers | ovary strigose; styles 1–1.3 mm, 2-fid at apex. |
|
Capsules | subglobose, 2–3 × 4 mm, sparsely strigose; columella 2–3 mm. |
|
Seeds | gray-green to gray-brown, globose-ovoid, 1.8–2.2 × 1.2–1.6 mm, longitudinally pitted; caruncle absent. |
|
Euphorbia | polycarpa is a highly variable species distributed throughout the Baja California peninsula, eastern Sonora, and the arid southwestern United States from southwestern Arizona to southern Nevada and central California. |
|
l | . |
|
c | . |
|
Wheeler | (1941) divided the species into seven varieties, the majority of which occur in Baja California Sur. |
|
He | reported two of these for the United States: var. hirtella and var. polycarpa. |
|
Variety | hirtella, as the name suggests, was applied to hairy plants. |
|
However | , it is here treated as a synonym of var. polycarpa, because variation in pubescence shows no geographic segregation and ranges along a continuum from glabrous or sparsely to densely hairy, and because glabrous and hairy branches can occur on the same individual. |
|
Cyathia | in terminal monochasia (thus appearing solitary at alternate nodes); peduncle 0.5–2.5 (or 10–25) mm, glabrous or sparsely strigose. |
|
Euphorbia polycarpa |
Euphorbia aaron-rossii |
|
Phenology | Flowering and fruiting spring–fall. | |
Habitat | Sandy soils and dunes, occasionally rocky slopes, riparian areas. | |
Elevation | 600–1300 m. (2000–4300 ft.) | |
Distribution |
AZ; CA; NV; nw Mexico
|
AZ |
Discussion | Varieties 5 (1 in the flora). Some of the varieties occurring in Mexico are highly divergent and appear to be sufficiently distinct to merit recognition as species. However, within the flora area, Euphorbia polycarpa is relatively uniform, and the only noteworthy variation involves the size of the involucral gland appendages. In the portion of the California Floristic Province occupied by E. polycarpa (Los Angeles, Orange, western Riverside, western San Diego, and Ventura counties) the appendages are conspicuously larger than those of plants throughout the remainder of its range in the southwestern United States (0.4–1.2 versus 0.1–0.3 mm). Large-appendaged plants are also common in Baja California and correspond well with the type collection. The taxonomic significance of this variation is not clear at this time, and the small-appendaged plants may merit segregation as an infraspecific taxon. However, no formal changes are proposed, awaiting a comprehensive review of the species throughout its range. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia aaron-rossii is restricted to the banks of the Colorado River in several small areas of the Grand and Marble canyons. The species is most closely related to E. strictior and E. wrightii, but due to its rarity, it has not been extensively studied. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 283. | FNA vol. 12, p. 242. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Subordinate taxa | ||
Synonyms | Chamaesyce polycarpa | |
Name authority | Bentham: Bot. Voy. Sulphur, 50. (1844) | A. H. Holmgren & N. H. Holmgren: Brittonia 40: 357, figs. 1, 2. (1988) |
Web links |