Cerastium texanum
Cerastium arcticum
Chihuahuan mouse-ear chickweed, Texas chickweed, Texas mouse-ear chickweed
arctic mouse-ear chickweed, céraiste arctique, mouse-ear chickweed
erect, sparingly branched proximally, slender, 15–35 cm, sparsely glandular-pilose; small axillary tufts of leaves absent.
erect, from decumbent base, 5–30 cm, sparsely to densely pubescent, hairs spreading, straight, often glandular; small axillary tufts of leaves usually absent.
not marcescent;
proximal blades broadly spatulate-petiolate, 8–55 × 3–16 mm, apex acute or obtuse, sometimes short-acuminate, softly pilose;
cauline few, sessile, blade linear-lanceolate to narrowly oblanceolate, 7–30 mm, apex acute, pilose.
subsessile;
blade broadly elliptic to obovate or rotund, larger blades in mid-stem region, 5–22 × 2–8 mm, apex round and obtuse, rarely broadly acute, pubescence ciliate and strigose, hairs long and eglandular, mixed with shorter eglandular hairs, colorless to somewhat fuscous;
proximal leaves not strongly marcescent, blade oblanceolate, often broadly so, spatulate.
very open and loose, 2–9(–25)-flowered cymes;
bracts narrowly lanceolate, pilose.
1–3-flowered, lax cymes, with patent, multicellular, long, glandular hairs;
proximal bracts broadly lanceolate, pubescence as leaves;
distal bracts narrowly lanceolate, margins narrow, scarious, glandular-pubescent.
straight, becoming sharply deflexed at base, slender, 5–20 mm, elongating in fruit, 1.5–4 times as long as sepals, glandular-pilose.
± straight or somewhat curved at apex, 5–45 mm, 1–4 times as long as sepals (rarely longer), pubescence long and glandular.
sepals green, turning pale orange-brown in fruit, lanceolate to ovate, 3–6 mm, margins narrow, apex acute, with short, glandular pubescence;
petals oblanceolate, 5–8 mm, 1.5–2 times as long as sepals, apex 2-fid;
stamens 5;
styles 5.
sepals narrowly lanceolate, 8–11 mm, margins narrow, apex acuminate, hairs ascending, long, glandular and eglandular;
petals 12–18 mm, 1–2 times as long as sepals, apex 2-fid;
stamens 10;
styles 5.
cylindric, straight, 5–12 mm, 1.5–2 times as long as sepals;
teeth 10, becoming outwardly coiled.
broadly conic, straight or almost so, 14–18 mm, 1.5–2 times as long as sepals, teeth 10, ± erect, margins convolute.
red-brown, 0.4–0.7 mm diam., tuberculate;
tubercles ± pointed;
testa not inflated.
red-brown, 1.1–1.3 mm diam., tuberculate;
tubercles acute;
testa not inflated, closely enclosing seed.
= 36.
= (54) 108.
Cerastium texanum
Cerastium arcticum
Cerastium texanum is exceptionally variable in flower and capsule size. The extent to which this variation is due to environmental conditions or is genic in origin is not known. The broad, spatulate basal leaves and the straight, cylindric capsule with its outwardly coiled (revolute) teeth distinguish this species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cerastium arcticum has been a much confused and misunderstood species, recently separated from C. nigrescens Edmonston ex H. C. Watson on seed characters. The latter has large seeds with loose, inflated testae, whereas C. arcticum has seeds that are smaller and have tight testae that cannot easily be removed (A. K. Brysting and R. Elven 2000). Much of the North American material previously placed in C. arcticum is now considered to belong to a distinct species, C. bialynickii Tolmatchew (see comments under that species). Cerastium alpinum differs from C. arcticum in having very long, flexuous, translucent hairs which often mat together. In C. arcticum and other members of the complex, the hairs are usually straight, yellowish, and not flexuous. Cerastium arcticum may on occasion have some pubescence like that of C. alpinum; such plants have been named C. arcticum var. vestitum. Whether they represent introgression of C. alpinum into C. arcticum, as suggested by E. Hultén (1956), is uncertain.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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