2(1). Ovaries several to many, borne on a broad to elongate receptacle, not 

 enclosed by the calyx (3) 



2. Ovaries one to many, becoming achenes that are covered by the calyx (5) 



3(2). Styles persistent and elongating after anthesis, plumose or jointed. .6. Geum 



3. Styles not elongate after anthesis, mostly deciduous (4) 



4(3). Receptacle dry, not greatly enlarged in fruit 5. Potentilla 



4. Receptacle pulpy and greatly enlarged in fruit 4. Duchesnea 



5(2). Calyx beset with hooked bristles, the 5-cleft limb closed after flowering and 

 persistent; petals yellow 8. Agrimonia 



5. Calyx not bristly, the 4 petaloid lobes greenish or rose-tinged; petals none 



9. Sanguisorba 



6(1). Ovary inferior, enclosed by and adnate to the calyx tube (hypanthium) 

 which becomes more or less fleshy; fruit a pome (applelike or 

 berrylike); calyx lobes more or less persistent at apex of fruit; 

 petals white (7) 



6. Ovary superior but sometimes concealed by the hypanthium; calyx tube not 



fleshy and enclosing the pistils or (if so) not adnate to them (8) 



7(6). Plants typically armed with strong woody spines; mature carpels hard and 

 bony, 1 to 5, free or coherent in the pulpy fruit 3. Crataegus 



7. Plants unarmed; mature carpels papery or soft-cartilaginous 2. Pyrus 



8(6). Calyx tube enclosing the numerous carpels, becoming fleshy; fruit (hip) 

 simulating a pome, crowned by the persistent calyx 10. Rosa 



8. Calyx tube not enclosing the carpels or not becoming fleshy (9) 



9(8). Fruit becoming juicy and more or less edible; stems usually armed with 

 prickles 7. Rubus 



9. Fruits much-inflated, not becoming juicy; stems without prickles 



1. Physocarpus 



1. Physocarpus Maxim. 

 About a dozen species, one in Manchuria, the others in North America. 



1. Physocarpus monogynus (Torr.) Coult. Mountain ninebark. 



Shrub usually less than 1 m. high, with usually decumbent stems and exfoliating 

 bark; branches brownish, glabrous to sparingly stellate-pubescent; leaves alternate, 

 with petioles 15 mm. long or less, suborbicular-ovate to reniform, usually deeply 

 palmately 3- or 5-lobed, incised, 1-4 cm. long, glabrous or nearly so and green 

 on both sides; terminal corymbs few- to many-flowered; bracts lanceolate, caducous; 

 pedicels 1-1.5 cm. long, usually sparingly stellate pubescent; hypanthium hemi- 

 spheric, about 3 mm. wide, stellate-pubescent; sepals 5, persistent, ovate-lanceolate 

 to elliptic, usually obtuse, densely stellate-pubescent on both sides; petals 5, white, 

 orbicular, spreading, about 3 mm. long; stamens 20 to 40, on a disk clothing the 

 mouth of the hypanthium; filaments long, slender, filiform; anthers didymous; 

 pistils 2 or 3, more or less united at the base; styles filiform, terminal; stigmas 

 capitate follicles 2 or 3, united to above the middle, densely stellate-pubescent, 

 3-5 mm. long, with ascending-spreading beaks, opening along both sutures; seeds 

 over 1.5 mm. long, usually 2, obliquely pyriform, shining, with a bony coat. 

 Opulaster monogynus (Torr.) O. Ktze. 



Rare on seepage ledges in canyons and on open or forested slopes in w. Okla. 

 (Cimarron Co.), the Tex. Trans-Pecos, N. M. (widespread) and Ariz. (Apache, 

 Cochise and Graham cos.), Apr.-June; from Tex. to S. D., Wyo., N. M. and Ariz. 



1016 



