31. Lyonothamnus A. Gray, Proc. Amer. Acad. Arts. 20: 291. 1885.
[For William Scrugham Lyon, 1851–1916, botanist, nurseryman, plant collector in California and Philippines, and Greek thamnos, bush or shrub]
Catalina or island ironwood
John L. Strother
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.
Species 1: California (Channel Islands).
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).
SELECTED REFERENCES Brandegee, T. S. 1890. The plants of Santa Catalina Island. Zoe 1: 107–115. Bushakra, J. M. et al. 1999. The extent of clonality and genetic diversity in the Santa Cruz Island ironwood, Lyonothamnus floribundus. Molec. Ecol. 8: 471–475. Erwin, D. M. and H. E. Shorn. 2000. Revision of Lyonothamnus A. Gray (Rosaceae) from Neogene of western North America. Int. J. Pl. Sci. 161: 179–193.
