404 ROSACEAE 



5. 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 usually 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-Uke; 

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

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



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

 more conic and the sepals reflexed; inflorescence shorter and more 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. pyramidala 

 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 (Xutt.) Rydb. 

 Densely cespitose and depressed undershrubs, with prostrate branches, 

 growing on rocks. Leaves oblanceolate or spatulate, entire, coriaceous, ev^er- 

 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 sutures; seeds linear. 



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

 flowers. 1. P. caespitosum. 



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, 1-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. Hypanthiiun 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; stjdes terminal; stigmas minute; ovules 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 silkj'-pubescent; sepals oblong, obtuse, 1.5 mm. long; petals narrowly spatu- 



