Proc. Amer. Assoc. Advancem. Sci. 4: 192. 1851.
Shrubs, 2–6 (–10) dm, herbage strigose, with appressed medifixed hairs. Stems 15–150, stiffly erect; bark dark russet, becoming gray, striate; long-shoots divaricately and oppositely branched, short-shoots present; unarmed (stiff dead branches resembling thorns). Leaves persistent (drought deciduous), cauline, opposite and clustered on short-shoots; stipules persistent on distal leaf-base margins, deltate-lanceolate, margins entire; petiole obscure; blade oblanceolate-spatulate, 0.6–1.2 cm, thickened, leathery, margins thick, rounded (not revolute), entire. Inflorescences terminal on long and short-shoot spurs, flowers solitary; bracts present, reduced, leaflike. Pedicels reduced. Flowers 11–14 mm diam.; epicalyx bractlets 0; hypanthium campanulate, 1–2 mm; sepals 4 (rarely 5), weakly spreading, abaxially yellow, outer narrowly ovate, inner broadly ovate, margins thin; petals usually 0, infrequently 1–4 (or 5) on scattered flowers, caducous, translucent yellow, spatulate; stamens (16–) 20–25 (–30), equal to sepals; torus extending into tubelike sheath surrounding ovary and proximal style (interior sericeous, exterior bearing some stamens); carpels 1 (rarely 2), glabrous except at style base, styles lateral, exserted beyond sheath, sericeous most of length; ovule 1, lateral. Fruits achenes, 1 (–2), brown, ovoid-reniform, distally narrower, 5.3–5.8 mm, shiny, glabrous; hypanthium persistent; sepals persistent, ascending. x = 8.
sw United States
Coleogyne is a xeromorphic desert shrub with floral features unusual within Rosaceae: a peculiar sheathlike torus surrounds the carpel and most of the style that bears some of the stamens, four sepals, and petals commonly absent but the inner sepal surface strongly yellow; vegetatively, Coleogyne is further distinguished by its opposite leaves and uniformly oriented medifixed trichomes. The single-ovuled, solitary ovary has a lateral style, suggesting relationship with multi-ovuled ancestors. Molecular data support relationships in the Kerrieae in subfam. Amygdaloideae (D. Potter et al. 2007).