264 NORTH AMERICAN FLORA [VoLumME 22 
or orbicular, 8-15 mm. long, rounded at the apex, abruptly narrowed into a very short 
winged petiole, crenate except at the base, bright-green and sparingly pubescent above, 
grayish-tomentose and slightly villous beneath; inflorescence 3-10 cm. long, simple or 
with a few short branches below, villous; sepals lance-ovate, acute, 1.5 mm, long; petals 
almost white, broadly ovate, obtuse, 2 mm. long; stamens about 20, 2 mm. long; pistils 
5; carpels about 2 mm. long, their beaks 1 mm. long. 
TYPE LOCALITY: Among granite rocks at Donner Pass, Nevada County, California. 
DISTRIBUTION: Nevada County, California. 
7. Sericotheca concolor Rydberg, sp. nov. 
Spiraea discolor dumosa S. Wats. Bot. Calif. 1: 170, in part. 1876. 
Holodiscus dumosus C. K. Schneid. Handb. Laudb, 1: 497, in part. 1905. 
A low shrub, less than 1 m. high, with spreading branches ; bark of young twigs light- 
brownish, villous; that of the older branches dark-brown, exfoliating; petioles obsolete ; 
leaf-blades cuneate-obovate, 5-12 mm. long, toothed above the middle with ovate teeth, 
rounded at the apex, cuneate at the base, almost equally finely and densely pubescent, 
almost velvety on both sides; inflorescence 5-8 cm. long, with few short spreading branches ; 
sepals broadly ovate, acutish, a little more than 1 mm. long; petals broadly ovate, about 
1.5 mm. long; stamens about 20, of about the same length as the sepals. 
Type collected on Mt. Davidson, Nevada in 1865, 7. Torrey 134 (herb. N. Y. Bot. Gard.). 
DISTRIBUTION: Mountains of northern and western Nevada and adjacent California; appar- 
ently the same also from the San Bernardino Mountains in southern California. 
8. Sericotheca microphylla Rydberg. 
Holodiscus microphylius Rydb. Bull. Torrey Club 31: 559. 1904. 
Hlolodiscus dumosus C. K. Schneid. Handb. Laudb. 1: 497, in part. 1905. 
A low diffuse shrub, 3-10 dm. high; bark of the young twigs light-brown or yellowish, 
soft-villous, that of the stems dark-brown or gray and exfoliating; leaf-blades spatulate- 
cuneate, 1-1.5 cm., rarely 2 cm. long, evenly serrate above the middle, obtuse at the apex, 
cuneate at the base and decurrent on the short petioles, finely pubescent and green above, 
white silky-villous and tomentose beneath ; inflorescence small, 3-5 cm. long, its branches 
few, short and few-flowered, spreading; sepals about 1 mm. long, ovate, villous; petals 
broadly obovate or oval, a little exceeding the sepals, stamens 20, about 1.5 mm. long. 
TYPE LOCALITY: Alta, Wahsatch Mountains, Utah. 
DISTRIBUTION : Mountains of Colorado, Wyoming, and Utah; apparently also in California. 
9. Sericotheca Schaffneri Rydberg, sp. nov. 
Spiraea discolor dumosa S. Wats. Proc. Am. Acad. 17: 353. 1882. 
? Schizonotus argeniteus griseus Kuntze, Rev. Gen. 226. 1891. 
A low shrub; bark of young twigs dark-brown, finely villous, that of the older branches 
almost black, exfoliating ; petioles 3-5 mm. long ; leaf-blades 1-3 cm. long, ovate or rounded- 
oval, obtuse at the apex, usually somewhat cuneate at the base and slightly decurrent on 
the petioles, more or less doubly serrate with ovate, mucronate teeth, sparingly pubescent 
on both sides, only slightly paler (not at all tomentose) and conspicuously glandular-atom- 
iferous beneath; inflorescence ovate, 5-7 cm. long, about 5 cm. wide, branched but 
branches usually simple, ascending-spreading; sepals ovate, acute, 1.5-1.75 mm. long; 
petals elliptic or oval, about 2 mm. long; stamens 15-20, about 2 mm. long; pistils 5; 
carpels semi-obovate, nearly 2 mm. long, with beaks scarcely 1 mm. long. 
Type collected at San Luis Potosi, Mexico, in 1879, W. Schaffner 451 (herb. N. Y. Bot. Gard.). 
DISTRIBUTION: Northern Mexico and Arizona, 
10. Sericotheca obovata Rydberg, sp. nov. 
A low bush, 1 m. or less high; bark of young twigs light-brown, villous, that of the 
older branches chestnut-brown or grayish, exfoliating; leaves 1.5-3 cm. long; leaf-blades 
rounded-obovate or spatulate, rounded at the apex, tapering below and decurrent on the 
short winged petioles, toothed above the middle with ovate, mucronate, simple teeth, thick, 
green on both sides, only slightly paler beneath, villous above, conspicuously glandular- 
