262 NORTH AMERICAN FLORA [VoLuME 22 
Leaves 8-15 mm. long; blades sparingly strigose above, round- 
crenate ; sepals lance-ovate, 1.5 mm. long. 6. S. saxicola. 
Leaf-blades cuneate at the base. 
Leaves almost equally finely and densely pubescent, almost vel- 
vety, on both sides. 7. S. concolor. 
Leaves finely pubescent and green above, white silky-villous and 
tomentose beneath. 8. S. microphylla. 
Leaves glandular-atomiferous and slightly hairy on the veins beneath, not 
at all tomentose. 
Leaf-blades more or less double-toothed, abruptly contracted at the base. 9. S. Schaffneri. 
Leaf-blades with simple teeth, cuneate at the base. 
‘Leaves 1.5-3 em. long, villous-pubescent above. 10. S. obovaia. 
Leaves 1-1.5 cm. long, glabrous or sparingly pubescent, 11. S. glabrescens, 
Teeth of the leaves lanceolate or triangular-ovate ending in a long mucro; 
achenes more or less convex on both edges, although more so on the 
lower ; stamens shorter than the sepals ; leaf-blades entire at the cuneate 
base. 
Leaves glabrous above ; upper edge of the carpels only slightly curved. 12, S. fissa. 
Leaves pubescent above ; upper edge of the achenes strongly curved. 
Leaves green and velvety above. 13. S. velutina. 
Leaves silvery-silky on both sides. 14. S. argentea. 
1. Sericotheca discolor (Pursh) Rydberg. 
Spiraea discolor Pursh, Fl. Am. Sept. 342. 1814. 
Spiraea ariaefolia Smith, in Rees, Cycl. 33: no. 16. 1819. 
Schizonotus discolor Raf. New Fl. 3: 75. 1838. 
Spiraea discolor ariaefolia S. Wats. Bot. Calif. 1: 170, 1876. 
Holodiscus discolor Maxim. Acta Hort. Petrop. 6: 254. 1879. 
Schizonolus argenteus ariaefolius Kuntze, Rev. Gen. 225. 1891. 
Schizonotus argenteus discolor Kuntze, Rev. Gen. 225. 1891. 
Schizonotus ariaefolius Greene, F), Fran. 58, in part. 1891. 
Schizonotus discolor ariaefolius Koehne. Deuts. Dendr. 265. 1893. 
Holodiscus ariaefolius Greene, Man. Bay Reg. 113. 1894. 
Holodiscus discolor ariaefolius Jepson, Fl. W. Middle Calif. 277, in part. 1901. 
Schizonotus discolor Purshianus Rehder, Cycl. Am. Hort. 1627. 1902. 
A shrub, 14.5 m, high; bark of the young twigs light-brown, more or less villous and 
tomentose; that of the older branches darker, chestnut or purplish, exfoliating; petioles 
1-2 cm. long, villous; leaf-blades rounded-ovate or oval, usually double-toothed with 
broadly ovate, mucronate teeth, acute at the apex, truncate, rounded or cuneate at the 
base, but slightly if at all decurrent, 4-10 cm. long, thin, green and sparingly pubescent or 
in age glabrate above, more or less densely villous and tomentose beneath, in the typical 
form white, but in the more common form (Spiraea ariaefolia) merely grayish; inflores- 
cence conicor ovate, 10-20 cm. long, 5-15 cm. wide, twice or thrice compound ; branches vil- 
lous, usually divergent; hypanthium small, saucer-shaped; sepals oblong or lance-oblong, 
obtuse or acutish, 1.25-1.5 mm. long; petals white, elliptic, 1.5 mm. long or more; stamens 
15-20, filaments 2-2.5 mm. long; pistils usually 5; carpels semi-ovate, straight on the 
inner, strongly curved on the outer margin, 1-5 mm. long with a beak of the same length. 
TYPE LOCALITY: Banks of the Kooskoosky. 
DISTRIBUTION : Hills and river-banks, from British Columbia to northern California, Idaho, 
and western Montana. 
ILLUSTRATIONS: Bot. Reg. 16: fl. 1365; Loud. Arb. f. 46, 447 (both as S. ariaefolia) ; 
Cycl. Am. Hort. /. 2269. : 
2. Sericotheca franciscana Rydberg, sp. nov. 
Spiraea discolor Brew. & Wats. Bot. Calif. 1: 170, in part. 1876. Not Sfiraca discolor Pursh. 
Schizonotus ariaefolius Greene, Fl. Fran. 58; in part. 1891. 
Holodiscus ariaefolius Greene, Man. Bay Reg. 113; in part. 1894. 
Holodiscus discolor ariacfolius Jepson, Fl. W. Middle Calif. 277, in part. 1901. 
A tall shrub, 2-7 m. high; bark of the young twigs rather dark-brown, villous and 
tomentose, that of the older branches more or less exfoliating ; petioles 5-10 mm. long, vil- 
lous ; leaf-blades thick, 3-6 cm. long, rounded-ovate, acute at the apex, rounded or truncate at 
the base, rarely somewhat cuneate, not decurrent, dark-green and densely pubescent (when 
young almost velvety) above, white villous and tomentose beneath, usually double-toothed 
with ovate, mucronate teeth; inflorescence conic or ovate, 5-15 cm. long, 5-10 cm. wide, 
twice or thrice compound, with divergent villous branches; bracts linear; hypanthium 
small, saucer-shaped; sepals ovate, acute, nearly 1.5 mm. long, thick; petals oval, white, 
