Petrophytum cinerascens
Rosaceae subfam. amygdaloideae
Chelan rockmat, halfshrub rockmat
prostrate to decumbent, 2–8 cm, internodes (0.1–)1(–2) cm.
blade oblanceolate to obtuse, 1–2.5(–3) × 0.2–0.4(–0.5) cm, palmately 3-veined, venation sometimes visible through hairs, apex obtuse, abaxial surface minutely canescent to strigose or cinereous, adaxial sometimes glandular.
alternate, sometimes opposite, simple, sometimes pinnately compound;
stipules present or absent.
sometimes branched, 2–8(–15) × 1–5 cm, canescent to puberulent;
bracts linear to oblanceolate, 5–10 mm, pilose.
0.5–2(–4) mm;
bracteoles 1(–2), extending from middle to apex of sepals, rarely beyond.
2–4(–6) mm diam.;
hypanthium 1 mm, canescent;
sepals erect, ovate or lanceolate, 1–1.5 mm, margins ciliate, abaxial surface pubescent, glandular;
petals oblanceolate or narrowly ovate, 1–2.5 mm, apex acute or rounded;
stamens 20–25, lengths 1.3 times petals (1.3–1.5 times sepals);
carpels (3–)5(–6), distinct.
torus absent or minute;
carpels 1–5(–8), distinct or +/- connate (Maleae), free or +/- adnate to hypanthium (many Maleae), styles distinct or +/- connate (some Maleae);
ovules (1 or)2(–5+), collateral, clustered, or biseriate.
follicles aggregated or not, capsules, drupes aggregated or not, aggregated drupelets, pomes, or aggregated nutlets, rarely achenes or aggregated achenes;
styles persistent or deciduous, not elongate (elongate in Gillenieae).
2 mm.
= 8, 9, 15, 17.
Petrophytum cinerascens
Rosaceae subfam. amygdaloideae
Of conservation concern.
Petrophytum cinerascens grows in crevices and ledges of outcrops above the Columbia River where there is little or no soil; it was found only on rocky outcrops of gneiss, schist, and granite between Chelan and Wenatchee in central Washington (D. J. Moore et al. 1998); C. L. Hitchcock et al. (1955–1969, vol. 3) erroneously cited its habitat as basaltic cliffs, which is the more common rock type on the Columbia River plateau. Moore et al. evaluated the ability of P. cinerascens for photosynthetic acclimation to increased growth temperature and drought stress under short-term experimental conditions, and concluded that it could not acclimate to such changes; they suggested that this endemic species might be at risk of extinction if warmer, drier local conditions result from projected climate changes.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cyanogenic glycosides are usually present in Amygdaloideae; sorbitol is present.
The name Amygdaloideae Arnott (1832) has priority over Spiraeoideae Arnott (1832), used by D. Potter et al. (2007), because Amygdalaceae (1820) is an earlier conserved name.
Tribes 9, genera 55, species ca. 1300 (9 tribes, 38 genera, 361 species, including 20 hybrids, in the flora)
(Discussion copyrighted by Flora of North America; reprinted with permission.)
WA
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