404 ROSACEAE 



6. S. idahoensis A. Nels. A shrub, 1-2 m. high, branched below; leaves 

 ovate or oval, rarely elliptic, serrate except the very base, 5-9 cm. long; 

 inflorescence paniculate, cylindric or pyramidal, dense, only slightly pubescent 

 on the branches; sepals reflexed, triangular-ovate; petals rose-colored, about 2 

 mm. long, ovate; follicles obovate-oblong. Mountains and foot-hills: Ida. 

 Submont. Au. 



6. S. Menziesii Hook. A shrub, 1-1.5 m. high; bark of the twigs brown 

 and \isually puberulent; leaf -blades elliptic, oblong, or oval, serrate above the 

 middle, acute, obtuse or rounded at either end, glabrous or puberulent on the 

 veins, 3-10 cm. long; inflorescence very dense, long and narrow, spike-like; 

 sepals pubescent, ovate; petals rose-colored, 1.5 mm. long; follicles glabrous. 

 Along streams: s Alaska — B.C. — Ore. — Ida. Submoiit. Je-Au. 



S. densiflora X Menziesii. Resembling most S. densiflora, but the inflorescence 

 more conic and the sepals reflexed; inflorescence shorter and m.ore open and leaves finer 

 serrate than in S. Menziesii. S. roseata Rydb. Ida. 



S. lucida X Menziesii. Intermediate between the two parents, having the leaf- 

 form of the former, the size of the plant and reflexed sepals of the latter ; inflorescence 

 intermediate, pyramidal and open and the petals white or pale pink. S. pyramidata 

 Greene. B.C. — Ida.— Ore. 



7. S. Douglasii Hook. A shrub, 1-2.5 m. high; bark of twigs brown and 

 more or less tomentose; leaf-blades elliptic, oblong, oval, or oblong-cuneate, 3-10 

 cm. long, serrate above the middle, dark green above, white-tomentose beneath; 

 inflorescence very long and narrow; sepals tomentose outside, ovate; petals 

 rose-colored, about 1.5 mm. long; follicles glabrous and shining. Lowlands: B.C. 

 — Calif. Submont. Je-Au. 



3. PETROPHYTUM (Nutt.) Rydb. 



Densely cespitose and depressed undershrubs, with prostrate branches, 

 growing on rocks. Leaves oblanceolate or spatulate, entire, coriaceous, ever- 

 green, crowded on the short branches. Inflorescence racemose, rarely compound. 

 Flowers perfect. Hypanthium hemispheric. Sepals 5, valvate. Petals 5, 

 imbricate, white. Stamens about 20; filaments filiform, distinct, about twice 

 as long as the sepals. Disk evident, entire, margined. Pistils 3-5; ovary and 

 lower part of the style very hairy; style filiform, terminal; ovules 2-4, pendulous. 

 Follicles leathery, dehiscent along both sutiu-es; seeds linear. 



Leaves spatulate, spreading; racemes short, 1-4 cm. long; bracts usually shorter than the 

 flowers. 1. P. caespilositni. 



Leaves narrowly oblanceolate, erect or ascending; inflorescence 4-10 cm. long, often 

 branched; bracts usually exceeding the flowers. 2. P. elatius. 



1. P. caespitosum (Nutt.) Rydb. Season's shoots very short; leaves 

 spatulate, 5-12 mm. long, 2-4 mm. wide, densely silky, l-ribbed, obtuse or mucron- 

 ate; sepals ovate-lanceolate, acute, 1.5 mm. long; petals spatulate, obtuse, 1.5 

 mm. long; follicles 3-5, 2 mm. long. Spiraea caespitosa 'Nutt. Rocks: (Black 

 Hills) S.D.—N.M.— Ariz.— Calif.— Ida.— Mont. Plain— Mont. Jl-S. 



2. P. elatius (S. Wats.) Heller. Shoots of the season often 2-3 cm. long, 

 erect; leaves silky, oblanceolate, acute, 1.5-2 cm. long, 3-4 mm. wide, usually 

 with more distinct petioles; sepals lanceolate, 2 mm. long, acute or acuminate; 

 petals oblanceolate, 2-3 mm. long. Spiraea caespitosa elatior S. Wats. Moun- 

 tains: Utah — Ariz. Son. — Mont. Jl-S. 



4. KELSEYA (S. Wats.) Rydb. 



Densely cespitose, pulvinate undershrubs, with short branches. Leaves 

 entire, crowded, leathery, persistent. Flowers perfect, solitary, almost sessile, 

 enclosed in the rosettes of the leaves. H>'panthiiUTi hemispheric. Sepals 5, 

 valvate. Petals 5, imbricate. Stamens about 10; filaments filiform, about 

 twice as long as the sepals; anthers didymous. Disk inconspicuous, entire. 

 Pistils about 5; styles terminal; stigmas minute; o\iiles 3-4, pendulous. Fol- 

 licles leathery, not inflated, opening along both sutures; seeds elongate-fusiform. 



1. K. uniflora (S. Wats.) Rydb. Leaves crowded, 2-3 mm. long, more'or 

 less silky-pubescent; sepals oblong, obtuse, 1.5 mm. long; petals narrowly spatu- 



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