Euphorbia exserta
Euphorbia yaquiana
coastal sand spurge, maroon or purple sand spurge
hairy Mojave spurge
erect or ascending, unbranched or branched, solitary, few, or occasionally densely clumped, previous year's dead stems not persistent, 20–33 cm, usually glabrous, rarely sparsely villous, glaucescent.
slender, erect or ascending, sometimes sinuous, densely branched near base, 10–50 cm, moderately to densely puberulent to lanulose.
alternate;
stipules less than 0.1 mm;
petiole (0–)1–3 mm, glabrous;
blade linear or linear-elliptic to obovate or orbiculate, proximal greatly reduced, scalelike, 15–30 × 1–20 mm, base cuneate to rounded, margins entire, apex rounded, broadly acute, or emarginate, surfaces glabrous, glaucescent;
venation often obscure on narrow leaves, midvein conspicuous.
petiole 0–1 mm;
blade usually lanceolate or elliptic-lanceolate, sometimes slightly oblanceolate, 8–30 × 6–14 mm, base usually acute, occasionally short-attenuate, rarely obtuse, margins entire, apex usually acute, occasionally obtuse, acuminate, or cuspidate, surfaces sparsely to moderately puberulent to lanulose;
venation pinnate, sometimes obscure, midvein prominent.
usually dark red, campanulate, 1.3–1.6 × 1.4–2.1 mm, glabrous;
glands 5, usually dark red, rarely greenish red, elliptic reniform, thickened, 0.3–0.5 × 0.8 mm;
appendages white or green, often forming narrow rim around distal margin of gland, 0–0.2 mm, entire.
campanulate to broadly turbinate, 2.2–3 × 2–2.5 mm, puberulent to lanulose;
glands 4, semicircular, trapezoidal, or elliptic-truncate, 0.8–1.5 × 1–2.2 mm, margins strongly crenate or dentate;
horns usually absent, if present then straight, 0.1–0.2 mm, generally equaling teeth on gland margin.
20–25.
12–20.
ovary glabrous;
styles 0.4–0.8 mm, 2-fid at apex.
ovary usually puberulent, occasionally lanulose;
styles 1–1.2 mm, 2-fid.
depressed-globose, 1.8–2.5 × 3.6–4.4 mm, glabrous;
columella 1.9–2.4 mm.
oblong-ovoid, 3.5–4 × 3–4 mm, 3-lobed;
cocci rounded, smooth, usually puberulent, occasionally lanulose;
columella 2.5–3 mm.
ashy white, ovoid, 2.1 × 1.3 mm, angled with 5 blunt longitudinal ridges, with shallow and irregular pits;
caruncle absent.
gray to whitish, oblong cylindric, 2–3 × 1.5–1.8 mm, irregularly shallowly pitted to almost smooth;
caruncle conic, 0.6 × 0.6 mm.
usually in terminal dichasia, sometimes pleiochasia;
peduncle 6–33 mm, filiform, glabrous.
peduncle 0.3–0.8 mm.
arrangement: terminal pleiochasial branches 3–5, each 1–2 times 2-branched;
pleiochasial bracts broadly ovate to subcordate, usually similar in size to, occasionally wider than, distal leaves;
dichasial bracts distinct, broadly ovate to almost reniform, base obtuse, margins entire, apex obtuse, acuminate to cuspidate;
axillary cymose branches 0–5.
Euphorbia exserta
Euphorbia yaquiana
K. R. Park (1998) recognized both Euphorbia exserta and E. gracilior as distinct species, with the former known only from the holotype. However, this treatment follows M. J. Huft (1997) and treats E. gracilior as a synonym of E. exserta. Although the type of E. exserta is unusual in having greenish red (versus dark red) cyathia and glands, as well as small gland appendages, it is otherwise typical of the species as a whole, including features such as the upright habit, reddish coloration, scalelike proximal leaves, and filiform peduncles to 30 mm that are also common to plants formerly treated as E. gracilior. Euphorbia gracilis Elliott, which has sometimes been applied to E. exserta, is an illegitimate name (a later homonym of E. gracilis Loiseleur-Deslongchamps) and pertains here.
The upright habit and usually dark red cyathia and glands distinguish Euphorbia exserta from the otherwise similar E. ipecacuanhae, while the glaucescent vegetative parts and smaller gland appendages readily separate E. exserta from the similar E. curtisii. Euphorbia exserta is found on the Gulf and Atlantic coastal plains.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Euphorbia yaquiana is endemic to Pima and Graham counties in southern Arizona and is known only from the Santa Catalina and Pinaleño mountains. Records of E. yaquiana from southwestern Colorado (as E. incisa var. mollis) likely represent misidentifications of E. brachycera; therefore, those disjunct occurrences have been excluded here from the distribution of E. yaquiana. Euphorbia yaquiana has often been treated as a synonym of E. schizoloba var. mollis, but molecular phylogenetic data show that it is more closely related to E. brachycera and E. chamaesula (J. A. Peirson et al. 2014).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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