310 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
New Mexico: Santa Fe and Las Vegas mountains; Sierra Grande; Sandia Moun- 
tains; Magdalena Mountains; Mogollon Mountains; Black Range; Sacramento Moun- 
tains. Transition Zone. 
A low shrub, not uncommon in the mountains at middle elevations. It should be 
valuable in cultivation because of its clusters of small white flowers, profusely 
produced. 
4. PETROPHYTON (Nutt.) Rydb. 
A densely cespitose depressed undershrub with prostrate branches; leaves spatulate, 
5 to 12 mm. long, 2 to 4 mm. wide, densely silky; peduncles 3 to 10 cm. high, with 
bractlike subulate leaves; inflorescence a dense spike of small whitish flowers; sepals 
ovate-lanceolate, acute, 1.5 mm. long; petals spatulate, obtuse, of about the same 
length as the sepals; follicles 3 to 5, 2 mm. long. 
1. Petrophyton caespitosum (Nutt.) Rydb. Mem. N. Y. Bot. Gard. 1: 206. 
1900. 
Spiraea caespitosa Nutt.; Torr. & Gray, Fl. N. Amer. 1: 418. 1840. 
Eriogynia caespitosa 8. Wats. Bot. Gaz. 15: 242. 1890. 
Tyre Locauity: ‘‘On high shelving rocks in the Rocky Mountains, toward the 
sources of the Platte.”’ 
Rance: California, Montana, and South Dakota to Arizona and western Texas. 
New Mexico: Big Hatchet Mountains; Guadalupe Mountains. Rocky hillsides, 
in the Upper Sonoran Zone. 
A rather rare plant, occurring on rocky cliffs and exposed tops of the mountains, 
where it spreads flat over the rocks, the roots finding their way into the crevices. 
It is to be expected in the south end of the Organ Mountains, for it has been collected 
in the Franklin Range just across the line in Texas. 
5. SERICOTHECA Raf. 
Shrub 2 or 3 meters high, with few main stems and numerous spreading branches 
bearing simple leaves and with terminal spreading panicles of small white flowers; 
leaves obovate-cuneate, decurrent, with a few rounded teeth, densely white-villous 
beneath; sepals 5, 1.5 mm. long, cream-colored like the hemispheric hypanthium; 
petals 5, elliptic or oval, about 2 mm. long; stamens about 20; pistils 5. 
1. Sericotheca dumosa (Nutt.) Rydb. N. Amer. Fl. 22: 263. 1908. 
Spiraea dumosa Nutt.; Torr. & Gray, Fl. N. Amer. 1: 416. 1840, as synonym; Hook. 
Lond. Journ. Bot. 6: 217. 1847. 
Holodiscus dumosus Heller, Cat. N. Amer. Pl. 4. 1898. 
Holodiscus australis Heller, Bull. Torrey Club 25: 194. 1898. 
Type Locauity: Rocky Mountains. 
Rance: Mountains of Wyoming and Utah to New Mexico and Chihuahua. 
New Mexico: Baldy; Santa Fe and Las Vegas mountains; Sandia Mountains; 
Magdalena Mountains; Mogollon Mountains; Black Range; Big Hatchet Mountains; 
San Luis Mountains; Organ Mountains; White and Sacramento mountains. Upper 
Sonoran and Transition zones. 
A beautiful and graceful shrub, producing an abundance of flowers. It is well 
worth cultivation and would doubtless grow well at middle elevations in the State. 
The type of Molodiscus australis was collected in Santa Fe Canyon by Heller (no, 
3840). 
6. POTENTILLA IL. Cinquerotn. 
Annual or perennial herbs, when perennial with elongated, scaly, more or less 
cespitose rootstocks; leaves pinnately or palmately compound; inflorescence usually 
cymose-paniculate; hypanthium concave, mostly hemispheric; bractlets, sepals, and 
petals 5; calyx persistent; stamens commonly 20; receptacle hemispheric or conic, 
bearing numerous (in P, lemmoni only 5 to 10) pistils; fruit of small achenes. 
