488 



ROSACEAE (ROSE FAMILY) 



smooth ; peduncles 1-3-flowered ; petals small, erect, white or pink ; fruit of 

 rather large juicy but acid drupelets. (JR. americanus Britton.) Wet woods, 

 etc., Lab. to Alaska, south w. to N. J., the Great L. region, n. la., and Neb. 

 Sepals and petals often 6-7. 



8. R. arcticus L. Stems suberect, 5-20 cm. high, filiform; leaflets 3(-5), 

 cuneate-obovate, rounded at the tip, somewhat firm, glossy above, coarsely ser- 

 rate-dentate ; petals rather large, spreading, rose-colored (rarely white) ; fruit 

 as in the preceding. Boggy places, Arctic Am., southw. to e. Que. and n 

 Minn. (Boreal and Arctic Eurasia.) 



5. EtlBATUS Focke. Armed (rarely unarmed} shrubs; stems biennial; 

 leaves on the first year's growth mostly 5-foliolate (pedate), on the flower- 

 ing canes chiefly 3-foliolate ; fruit not separating from the juicy receptacle, 

 blackish when ripe (reddish in no. 34). BLACKBERRY. A group of great 

 taxonomic difficulty, in which many species have been recently proposed. 

 Of these, the better marked have been here freely included, but without 

 entire confidence that future intensive study may not show them to be 

 mtergradient and perhaps in some cases hybrid forms. 



a. Canes erect or arched-ascending b. 



b. Pedicels habitually unarmed, often pubescent or glandular-hispid, 



rarely with a few weak bristles c. 

 C. Pedicels copiously glandular-hispid. 



Leaflets appressed-villous above ; prickles of the stem stoutish 9. R. alltghenientit. 

 Leaflets glabrous above ; prickles of the stein setiform rather 



than thorn-like. 



Petioles of the 5-foliolate leaves scarcely or not at all glandu- 

 lar, copiously armed with hooked prickles ; leaflets rhom- 

 bic-lanceolate or narrowly ovate. 



Lower surface of the leaflets velvety to the touch . . 10. 

 Lower surface of the leaflets essentially glabrous . . . 11. 

 Petioles of the 5-foliolate leaves copiously glandular-pubes- 

 cent, weakly armed. 



R.Jiacinanut. 

 R.junceus. 



R. glaniiicauli*. 

 R. fronditentit. 



R. frondotut. 

 R. pergratut. 



Fruit of 30-60 small drupelets 12. 



Fruit of few large drupelets 13. 



c. Pedicels glandless or with only occasional gland-tipped hairs d. 

 d. Lower surface of leaflets even at maturity downy to the touch . 

 e. Inflorescence numerously flowered, at length elongated and 



more or less cylindrical. 



Inflorescence provided with 4-6 nnifoliolate petioled bracts 14. 

 Inflorescence with 1-2 unifoliolate petioled bracts . . 15. 

 e. Inflorescence mostly fewer-flowered, corvmbifortn. 



Canes erect or nearly so ; teeth of the leaflets deltoid-ovate, 

 mucronulate-acuminate ; prickles of stem few, weak, 



1-2 mm. long 16. R. satirus. 



Canes commonly recurved and often rooting at tip ; teeth 

 of leaflets lanceolate, narrowly acuminate ; prickles of 



stem mostly 3-6 mm. long 17. R. recurvant. 



d. Lower surface of leaflets glabrous, glabrate, or nearly so. 



Internodes of main stem and petioles of 5-foliolate leaves 



armed with numerous slender or bristle-formed prickles. 



Prickles chiefly or exclusively on the angles ; leaflets of the 



mature 3-foliolate leaves small, rarely over 5 cm. long . 18. R. tlrgantulut. 

 Prickles on the faces as well as the angles of the stem ; leaf- 

 lets of the 3-foliolate leaves larger, often 6-8 cm. long . 19. R. pecvliarit. 

 Internodes and petioles with few prickles or unarmed. 



Inflorescence corymbiform 20. It. Ramlii. 



Inflorescence racemiform, subcylindric 21. R. canaden-sit. 



b. Pedicels armed with stoutish or slender but pungent bristle-formed 

 prickles /. 



/. Leaflets laciniate-cleft ; introduced 22. J?. laciniatus. 



/. Leaflets not laciniate-cleft g. 

 ff. Lower surfaces of the leaflets velvety to the touch. 



Leaflets white-tomentose beneath . . . . . . 23. R. cunfifoliut. 



Leaflets green or merely prayish beneath. 

 Prickles of the first year's growth rigid. 

 Pedicels copiously glandular-pubescent . . . .24. R. Andrewttianu* 



Pedicels tomentu'lose but not glandular. 

 Stems rigid, not rooting at the tip ; prickles on the 



first year's growth 6-7 mm. long . . . .25. R.florioomu*. 



Stems flezuous, often rooting at the tip ; prickles on 



the first year's growth 2-5 mm. long . . .26. R. Jeckytanu* 

 Prickles on the first year's growth numerous, weak, bristle- 

 formed, on the surfaces as well as the angles of the stem 27. R. abbreviam. 



