Trifolium amoenum
Trifolium trichocalyx
showy Indian clover, two-fork clover
Monterey clover
erect, branched from base and distally, or unbranched.
prostrate, decumbent, or erect, branched.
palmate;
stipules ovate-oblong, 0.5–1.8 cm, margins entire, toothed, or irregularly lobed, apex acuminate;
petiole 0.5–10 cm;
petiolules to 1 mm;
leaflets 3, blades broadly obovate or elliptic, 1.7–3.3 × 1.1–2 cm, base cuneate, veins fine, margins entire or denticulate, apex rounded, obtuse, or retuse, surfaces pilose, abaxial less so.
palmate;
stipules ovate, 0.4–1.2 cm, margins serrate-lacerate, apex acuminate;
petiole 1–4 cm;
petiolules 0.5 mm;
leaflets 3, blades obovate, 0.5–1.5 × 0.4–1 cm, base cuneate, veins moderately prominent, margins denticulate, apex truncate, retuse, or mucronulate, surfaces glabrescent.
terminal or axillary, 30–50-flowered, bluntly conic, ellipsoid, globose, or subglobose, 1.5–3 × 1.5–2.5 cm;
involucres absent.
axillary or terminal, 2–15-flowered, subglobose, 1.5–1.8 × 0.5–1.5 cm;
involucres flattened or vase-shaped, 1–3 mm, when folded, not hiding flowers except proximally, incised 2/3–3/4 their length, lobes 5–15, linear-lanceolate, entire, acuminate.
5–15 cm.
1.5–4 cm.
absent;
bracteoles cuplike, to 0.5 mm.
erect, 1.5 mm;
bracteoles absent.
13–16 mm;
calyx tubular, 9–12 mm, pubescent, veins 20–30, tube 3 mm, lobes nearly equal, appearing rigidly erect, linear-setaceous, plumose, sinuses acute, orifice open;
corolla white to pink with purple tips, 12–16 mm, banner ovate-oblong, 12–15 × 4 mm, apex broadly rounded, emarginate.
8–11 mm;
calyx campanulate-tubular, not slit between adaxial lobes, 6–9 mm, usually densely pubescent, rarely sparsely so, veins 10, tube 2.5–4.5 mm, lobes unequal, lanceolate-subulate, orifice open;
corolla light purple with darker purple keel petals, 6–10 mm, banner narrowly obovate, 4–5 × 1 mm, apex retuse.
obovoid, 4 mm.
sessile, oblong, 5 mm.
1, dark brown, ellipsoid, 2–3 mm, smooth.
3–6(–9), pale brown, mottled purple, globose to mitten-shaped, 0.8–1 mm, smooth to slightly roughened, semiglossy.
Trifolium amoenum
Trifolium trichocalyx
Trifolium amoenum was considered extinct (J. P. Smith Jr. 1984) but was rediscovered in 1993 (P. G. Connors 1994). Specimens of T. amoenum are known from Marin, Napa, San Mateo, Solano, and Sonoma counties; it appears to be extant in only single populations in each of Marin and Solano counties. Allozyme studies of the two known populations revealed fixed genetic differences between them (E. E. Knapp and Connors 1999).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Trifolium trichocalyx is an extremely rare species known only from Mendocino and Monterey counties. D. I. Axelrod (1982) suggested that T. trichocalyx might have originated as a hybrid between T. microcephalum and T. variegatum, but this is not supported by molecular studies (N. W. Ellison et al. 2006). It appears to be fire-adapted and appeared in large numbers shortly after a fire in 1987 (U.S. Fish and Wildlife Service 2004).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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