390 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



17. Flowers solitary or in few-flowered cymes or fascicles (18). 

 18. Style wholly deciduous from the mature achene; leaves 

 pinnately compound; bark exfoliating; flowers showy, 

 the petals bright yellow 11. Potentil-la. 



18. Style persistent; leaves simple but sometimes deeply cleft 

 or pinnatifid (19). 

 19. Petals normally none (exceptionally present in Coleo- 

 gyne); leaf blades entire or merely dentate; pistil 

 solitary (20). 

 20. Pistil not enclosed in a sheath; style terminal, not 

 twisted or bent, in fruit greatly elongate and plu- 

 mose nearly to the apex 16. Cercocarpus. 



20. Pistil at anthesis enclosed in a thin sheathlike pro- 



longation of the disk; style lateral, much twisted 

 and bent, villous only near the base. 



17. COLEOGYNE. 



19. Petals present; leaf blades wedge-shaped, usually deeply 

 cleft or pinnatifid (21). 



21. Style not greatly elongate or plumose in fruit, stout, 



beaklike; petals spatulate, cream-colored or yellow; 



pistil solitary or rarely 2 18. Purshia. 



21. Style greatly elongate and plumose in fruit; petals 

 broadly obovate or nearly orbicular, white; pistils 

 several or numerous (22). 

 22. Bark exfoliating; bractlets present, alternating with 

 the sepals; achenes with purplish tails. 



14. Fallugia. 



22. Bark not exfoliating; bractlets none; achenes with 



white tails 15. Cowania. 



1. PHYSOCARPUS. Ninebark 



Plant a small shrub, with bark exfoliating in strips; leaves simple, 

 petioled, the blades palmately lobed; flowers in terminal corymbs; 

 petals 5, these and the numerous stamens inserted on the throat of the 

 calyx; pistils 1 to 5, short-stipitate, becoming inflated few-seeded 

 capsules dehiscent on both sutures. 



1. Physocarpus monogynus (Torr.) Coult., Contrib. U. S. Natl. 

 Herbarium 2: 104. 1891. 



Spiraea monogyna Torr., Ann. Lye. N. Y. 2: 194. 1827. 

 Opulaster monogynus Kuntze, Rev. Gen. PL 2: 949. 1891. 



White Mountains (Apache County), Pinaleno Mountains (Graham 

 County), Cliiricahua Mountains (Cochise County), 8,000 to 9,500 

 feet, pine and spruce forests, June. South Dakota to Texas, eastern 

 Arizona, and Nevada. 



2. SPIRAEA 



A small undershrub, or the numerous stems woody only at base, 

 forming mats; leaves with small spatulate entire blades; flowers many 

 in very dense, simple or sparingly branched spikelike inflorescences 

 terminating the few-bracted scapes; stamens numerous; pistils few, 

 becoming follicles (dehiscent on one suture). 



1. Spiraea caespitosa Nutt. ex Torr. and Gray, Fl. North Amer. 1: 

 418. 1840. 



Petrophyton caespitosum Rydb., N.Y. Bot. Gard. Mem. 1: 206. 

 1900. 



Navajo, Coconino, and Yavapai Counties, also Huachuca Moun- 

 tains (Cochise County), 5,000 to 8,000 feet, common on both rims of 



