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FNA | Family List | FNA Vol. 9 | Rosaceae | Holodiscus

2b. Holodiscus microphyllus Rydberg var. sericeus F. A. Ley, Bull. Torrey Bot. Club. 70: 283. 1943.

Short-shoot leaf surfaces sessile- and/or stipitate-glandular (often obscured by hairs), abaxial white, sometimes silvery white, veins, intercostal regions, and margins obscured by hairs, densely sericeous, white granular deposits sparse, adaxial white short-villous. Inflorescences 2–6 × 1–4 cm. Pedicels 2–3 mm. Flowers: nectar disc sparsely white-hirsute; sepals densely white-tomentose, usually eglandular; petal base abaxially with few, scattered long hairs.

Flowering Apr-–Jun. Rock outcrops, often limestone, sandy loam soil derived from diorite, margins of ponderosa pine woodlands, Jeffrey pine forests, pinyon pine-juniper woodlands; 1500–3000 m; Ariz., Calif., Nev.; Mexico (Baja California).

The unusually dense, white to silvery white, sericeous indumentum that characterizes var. sericeus is found only in northwestern Arizona, extreme southern Nevada, some desert mountains of southern California, and northern Baja California, Mexico. In this region, var. microphyllus also occurs but its populations are usually disjunct. The primary problem in distinguishing var. sericeus arises when specimens actually belong to var. microphyllus but are abaxially off-white to light gray and tomentose to villous.


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