126 ROSACEAE 



Prickles of the inflorescence not flattened, straightish; leaflets dark 

 green above, acuminate, with small teeth; stem usually dark bluish, 

 with a bloom. 9. R. occidentalis. 



Prickles of the inflorescence strongly flattened and curved; leaflets 

 yellowish green above, acute, with coarse teeth; branches usually 

 straw-colored. 10. R. leucodermis. 



Inflorescence racemose; fruit red; leaves, when ha\Tiig more than 3 leaflets, 

 pinnately compound. 

 Plant not at all glandular-hispid; inflorescence with weak prickles, 

 villous. 11. R. melanotrachys. 



Plant more or less glandular-hispid, especially in the inflorescence. 



Sepals narrowly lanceolate, gradually acuminate; leaves glabrate 

 beneath in age. 

 Stem sparingly bristly; leaflets neither strongly pUcate nor 



strongly veined. 12. R. peramoenus. 



Stem densely bristly; leaves strongly plicate and strongly veined. 



13. R. viburnifolius. 

 Sepals ovate or ovate-lanceolate abruptly acuminate. 



Young stems, petioles, and irflorescence neither densely tomen- 



tose nor puberulent. 14. R melanolasius. 



Yoimg stems, petioles and inflorescence densely toraentose or 

 puberulent. 15. R. acalyphaceus. 



Carpels coherent to the fleshy receptacle; plant dioecious with decumbent stems 

 and 1-3-foUolate green leaves. 16. R. macropetalus. 



36. ROSA (Toiirn.) L. Rose. 



Pistils numerous; styles as well as the upper part of the hypantliium persistent; sepals 

 in fruit erect or ascending, persistent. 

 Infrastipular prickles not present; branches mostly unarmed and young shoots bristly, 

 but not prickly. 

 Inflorescence corymbose, terminating the stems (or rarely the branches) ; plant 

 suffruticose; stem usually dying back to near the ground; leaflets 9-11. 

 Leaves glabrous or nearly so. 



Leaflets mostly 2-5 cm. long, not glaucous, decidedly acute; plant 3 dm. 



high or more; flowers corymbose. 1. R. arkansana. 



Leaflets rarely more than 2 cm. long, mostly rounded at the apex, some- 

 what glaucous beneath; plant 1-2 dm. high; flowers 1-3. 



2. R. Lunellii. 

 eaves densely pubescent, especially beneath. 

 Upper stipules and bracts not densely glandular; leaflets 1..5— i cm. long; 



plant 3-5 dm. lugh. 3. R. suffulla. 



Upper stipules and bracts densely glandular; leaflets seldom more than 

 1.5 cm. long; plant 1-3 dm. liigh. 4. R. alcea. 



Inflorescence of solitary or few corymbose flowers at the end of lateral branches; 

 plant shrubby; leaflets usually 5 or 7, or 9 only on the young shoots. 

 Hypanthium decidedly pear-shaped or elliptic, acute at the base, with a dis- 

 tinct neck at the top. 

 Sepals rarely more than 1 cm. long; bark yellowish green. 5. R. collaris. 

 Sepals 2-3 cm. long; bark brown. 



Leaflets conspicuously glandular-granuhferous, but scarcely at all hairy 

 beneath, rounded-oval, double-toothed. 6. R. Engelmannii. 



Leaflets densely pubescent, but rarelj slightly if at all glandular-gran- 

 uhferous beneath, mostly elUptic, simple-toothed. 



7. R. acicularis. 

 Hypanthium subglobose, almost without a neck. 8. R. Bourgeauiana. 



Infrastipular prickles usually present. 



Flowers mostly solitary; petals usuaUy 2.5 cm. long or more; fruit 12-20 mm tliick. 

 Prickles straight or nearly so. 



Hypanthium densely prickly. 9. R. MacDougali. 



Hypanthium not prickly or rarely slightly so. 



Leaflets more or less double-toothed, more or less glandular-granulifer- 

 ous beneath; stipules and racliis glandular. 

 Leaflets very thin, pale and shghtly glandular-granuhferous, but 



not muriculate beneath. 10. R. nutkana. 



Leaflets tliicker, dark green on both sides, conspicuously glandular- 

 muriculate beneath. 11. R. muriculala. 



Leaflets simple-toothed, puberulent but not glandular-granuhferous 

 beneath; rachis rarely glandular. 12. R. Spaldingii. 



Prickles more or less distmctly curved. 

 Hypanthium prickly. 



Stem stout, 1 m. liigh or more; leaflets usually more than 3 cm. long. 



13. R. Underwoodii. 

 Stem low, usually less than 3 dm. high; leaflets usually not more than 



2 cm long. 16. R. aciculata. 



Hypantliium smooth. 



Prickles very large and flat; twigs densely glandular and pubescent. 



14. R. Durandii. 

 Prickles short and slender, not conspicuously flattened; twigs not con- 

 spicuously glandular, mostly glabrous. 



Leaflets perfectly glabrous or merely glandular-granuhferous be- 

 neath. 



