Euphorbia serpens Kunth, matted sandmat, creeping spurge. Annual, taprooted, several—many–stemmed at base, mat–forming, branches diverging at 20—30° (to 90° in late summer and fall), prostrate, rooting at nodes, typically < 3 cm tall; monoecious; shoots strongly 2–dimensional (plagiotropic), glabrous, glaucous; latex, white, copious; adventitious roots where present mostly 1 or 2 per node.
Stems cylindric, to 1.5 mm diameter, flexible, green becoming tannish or pinkish above, internodes 10—30(—35) mm long (1—10 mm on late–summer and fall growth), node swollen ca. 2× stem diameter.
Leaves opposite decussate, simple, short–petiolate, with stipules; stipules 2 (4 per node), attached to node and pairs fused across node, fused stipules broadly triangular, 0.5—1 × 1 mm, white–membranous, entire or jagged to fringed; petiole 0.4—1 mm long, curved to orient leaves horizontally, greenish aging pinkish; blade broadly ovate or heart–shaped to oblong or roundish, 1.3—7 × 1.1—5 mm, oblique and rounded to cordate at base, entire, obtuse to rounded or slightly notched at tip, typically 1–veined, gray–green but commonly reddish on margins.
Inflorescence cyathium (= involucre with staminate flowers and 1 pistillate flower), axillary, produced in leafy, cymelike arrays; peduncle 0.7—1.5 mm long, gradually expanded into base of involucre; cyathium 0.7—0.9 mm wide (including spreading glands and appendages); involucre narrowly inversely conic, ± 1 × 0.6 mm, green, white to light pinkish on margins and below glands, externally glabrous, internally hairy below glands, with 5 bracts and 4 glands, the bracts of involucre fused most of length, fringed, acute to acuminate or 3–toothed at free tips with white margins, the glands alternate with bracts (1 absent), nectar–producing, raised, transversely elliptic to oblong, 0.1 × 0.2—0.4 mm, fleshy, reddish to burgundy, depressed in center, appendaged below gland, the appendage petal–like, > gland, white, scalloped on outer margin; staminate flowers 5—7(—10) in 5 clusters of 1(—2), each with pedicel–like stalk, each cluster associated with a bractlet; bractlet lanceolate to oblanceolate, 0.5—0.7 mm long, white, fringed, pedicel at anthesis ± 1 mm long; pistillate flower on a pedicel–like stalk (gynophore), at anthesis gynophore short and erect, with only styles exposed, soon after gynophore elongating and becoming recurved with maturing ovary exserted, with 3 whitish, acute lobes at base of ovary.
Staminate flower reduced to 1 stamen; filaments ± 0.2 mm long; anther conspicuously dithecal, each sac spheroid, < 0.3 mm long, pale yellow to yellow–green and reddish burgundy on margins of slit, becoming rose–tinged to reddish burgundy on faces, longitudinally dehiscent; pollen golden yellow to pale yellow.
Pistillate flower reduced to 1 pistil; ovary superior, 3–lobed broadly ovoid, ± 0.5 mm long, light green aging with pink to reddish edges, glabrous, 3–chambered, each chamber with 1 ovule; styles 3, 0.3—0.4 mm long, 2–branched at midpoint, the branches cylindric, fleshy, light green below and pink or reddish at tip; stigmas minute.
Fruit capsule, 3–seeded, 3–lobed and broadly triangular–ovoid, 1.5—1.7 × 1.7—1.9 mm, glabrous, elastically dehiscing along septa and chambers into 6 dry valves (some valve–pairs) remaining attached at base) and expelling seeds.
Seed quadrangular–oblong, 1—1.2 × 0.6—0.8 mm, orangey brown beneath frosty–white, very finely netted epidermis, grooved on obtuse ridge, acute on dorsal ridge, rounded on lateral angles, oily when poked.
A. C. Gibson & B. A. Prigge