20. Euphorbia stictospora Engelm. (mat spurge)
Chamaesyce
stictospora (Engelm.)
Small
Map 1682, Pl.
382 a–c
Plants annual,
with taproots. Stems 5–45 cm long, usually prostrate, occasionally with
ascending tips, several- to many-branched, the branches often overlapping
(plants mat-forming), not flattened toward the tip, usually yellowish brown
(sometimes slightly reddish-tinged), densely and evenly pubescent with
spreading hairs. Leaves opposite, sessile or very short-petiolate. Stipules
small scales 0.5–1.2 mm long, these not fused or, on 1 side of the stem, those
from the adjacent leaf in each pair fused toward the base into a single small
structure positioned between the leaf bases, variously entire to irregularly
toothed or fringed. Leaf blades 3–10 mm long, oblong to oblong-obovate or
occasionally nearly circular, asymmetrical at the base with the side toward the
stem tip usually angled or rounded and the other side more or less truncate and
expanded into a small, rounded auricle, broadly rounded to bluntly pointed or
occasionally shallowly notched at the tip, the margins minutely or more deeply
several-toothed (best observed with magnification), the upper surface sparsely
to moderately pubescent with more or less spreading hairs and lacking a reddish
spot, the undersurface moderately to densely pubescent with more or less
spreading, slender hairs, often somewhat lighter green than the upper surface. Inflorescences
axillary, of solitary cyathia or appearing as small clusters on short axillary
branches. Involucre 0.7–1.0 mm long, moderately to densely hairy on the outer
surface, the rim shallowly 5-lobed, the marginal glands 5, 0.1–0.3 mm long and
often somewhat unequal in size, the body oblong, green to reddish purple, with
a relatively inconspicuous petaloid appendage 0.1–0.3 mm long, this white to
strongly pinkish- or reddish-tinged. Staminate flowers 3–9 per cyathium.
Ovaries hairy, the styles 0.2–0.5 mm long, each entire or inconspicuously
notched at the very tip. Fruits 1.5–2.3 mm long, moderately to densely
pubescent with more or less spreading hairs, especially toward the angles.
Seeds 1.0–1.5 mm long, oblong-ovate to ovate in outline, angular in
cross-section, concave at the base, the surface finely pitted, some of the pits
rarely forming shallow, irregular troughs and the seeds then appearing
partially and irregularly few-ridged, light to dark brown, usually mottled,
sometimes with a thin, white coating, this often wearing away irregularly,
lacking a caruncle. July–October.
Introduced, uncommon,
known only from historical collections from Jackson County (Arizona to Texas
north to Wyoming and Iowa; Mexico; introduced sporadically east to New York).
Dry, open, disturbed areas.