Lyonothamnus

Plants clonal, 50–100(–150) dm, herbage usually glabrous, glabrate, or tomentulose (glabrescent). Stems 1+; bark brown or gray; short shoots absent. Leaves tardily falling, cauline; stipules absent or lance-linear, margins entire; petiole present; blade simple (sometimes lobed), palmate, or pinnate, simple blades or leaflets elliptic, lance-linear, lanceolate, or oblong, 6–18 cm, leathery, leaflets 3–7, usually pinnately lobed, margins ± revolute, entire, crenulate, or serrate. Inflorescences terminal, 50–800+-flowered, compound corymbs or panicles; bracts present; bracteoles present. Pedicels present. Flowers produced after leaves, (5–)6–8 mm diam.; hypanthium 3–4(–5) mm (including sepals), exterior tomentulose, interior pilose; sepals 5, spreading, ovate to triangular; petals 5, white, obovate to orbiculate; stamens (12–)15+ in 1 series, shorter or longer than petals; carpels tomentulose. Fruits aggregated follicles, 2(–3), ± ovoid to lanceoloid, 3–4 mm (excluding styles), stipitate-glandular, dehiscent adaxially; hypanthium persistent; sepals persistent or tardily falling, ± spreading. Seeds 2–4+, ± ellipsoid to fusiform, firm, ends rounded or truncate, faces smooth or minutely papillate, seed coats tight. x = 9.

Distribution

Calif. (Channel Islands).

Discussion

Species 1.

Taxonomically, Lyonothamnus has been moved about within Rosaceae; here it is placed as an isolated taxon within Amygdaloideae. It is known from Miocene fossils from California, Nevada, and Oregon (D. M. Erwin and H. E. Shorn 2000).