37. Rhodotypos Siebold & Zuccarini, Fl. Jap. 1: 185, plate 99. 1841.
Black jetbead [Greek rhodon, rose, and typos, pattern, alluding to resemblance to genus Rosa]
Shrubs, ˂spreading˃, rounded, 5–20(–30) dm. Stems 5–20+, widely arcuate; bark gray; long shoots moderately branched; unarmed; glabrous. Leaves deciduous, cauline, opposite; stipules deciduous, linear, margins entire; petiole present; blade ovate, 4.5–10 cm, membranous, margins flat, sharply doubly serrulate, ˂teeth sometimes stipitate-glandular along distal margins˃, surfaces sparsely sericeous. Inflorescences terminal ˂on vernal, leaf-bearing branches˃, flowers solitary; bracts absent. Pedicels present. Flowers 30–45 mm diam.; epicalyx bractlets 4, ˂slender˃; hypanthium shallowly cupped, 4–6 mm diam., exterior sericeous-strigose; sepals 4, spreading, ovate to oblong-ovate; petals 4, ˂spreading-ascending˃, white, ovate-orbiculate, ˂base short-clawed, apex rounded˃; stamens 30–60 (± in 4 clusters), much shorter than petals; torus thickened, dome-shaped, surrounding and overtopping ovaries, constricted below styles, leaving styles free, distally crenulate or 4-toothed; carpels 4, glabrous, styles lateral; ovules 2. Fruits aggregated nutlets (appearing as dry drupelets), 1–4, ˂black˃, ovoid-globose, compressed, 6–9 mm; ˂exocarp thin; mesocarp dry, thin; endocarp thick, cartilaginous˃; hypanthium persistent; sepals persistent, reflexed. x = 9.
Species 1: introduced; e Asia.
Rhodotypos is an Asian mesophytic shrub that shares several characteristics with the western North American desert shrub Coleogyne, including opposite leaves, 4-merous, terminal, solitary flowers, ovaries with lateral (adaxial) styles, and a distinctive inner, rimlike or sheathlike torus extension that surrounds the ovaries and occasionally bears some of the stamens. The fruit of Rhodotypos is drupelike during development, but dries at maturity while retaining a shiny, smooth exocarp; it can be considered a modified drupelet.
With Coleogyne, Kerria and Neviusia, they form Kerrieae of subfam. Amygdaloideae, an alliance recognized by G. K. W. Schulze-Menz (1964) but in the Rosoideae.