118 BIcKNELL: FERNS AND FLOWERING PLANTS OF NANTUCKET 
or more slender and 5 mm. long, straight and erect or slightly 
retrorse, usually broader-based, decurved, and often numerous 
on the petioles and flowering branchlets; primary leaves 6-10 cm. 
long, mostly 5-foliolate, on strongly armed, thinly pubescent 
petioles; leaflets thickish and dark green, often rugose, loosely 
appressed-pubescent on the upper surface, paler and softly 
short-pubescent beneath, dentate-serrate with very mumer- 
ous acute teeth; odd leaflet broadly ovate to orbicular, even 
broader than long, rounded or cordate at base, short-acuminate, 
becoming 7 cm. long and 6.5 cm. broad, but often smaller, its 
petiolule 2.5-3.5 cm. long; middle pair mostly elliptic-obovate, 
rounded or somewhat narrowed towards the base, on short foot- 
stalks 2-10 mm. long, the basal pair broadly elliptic; flowering 
branchlet$ numerous, often erect along prostrate stems, leafy, 
mostly 10-20 cm. long, angled and becoming stout and stiffly 
flexuous, somewhat  villous-tomentose, often strongly armed; 
their trifoliolate leaves mostly 3 or 4, on rather short petioles, suc- 
ceeded above by 3-5 conspicuous, short-petioled, orbicular or sub- 
orbicular, often cordate, incised or lobed unifoliate leaves subtend- 
ing the pedicels; inflorescence a short, corymbose, leafy-bracted 
_ raceme, sometimes descending by  slender-pediceled axillary 
flowers or rudimentary corymbs to the base of the branch- 
let; pedicels erectly ascending, 2-4 cm. long, with the calyx 
villous-tomentulose, armed with rather stout, spreading or 
slightly decurved prickles; calyx lobes sometimes sparingly setu- 
lose, often with foliaceous prolongation; flowers full-petaled, 
becoming 4 cm. wide; petals oblong to obovate. 
Local by roadsides and borders of thickets, especially along 
the Quidnet and Wauwinet roads, near Polpis and in Pocomo; 
Siasconset; one cluster by the roadside near the old mill. First 
flowers June 12, 1909; in full flower June 16-24, 1910. A note- 
worthy blackberry, well characterized among the semiprostrate 
forms by its straight, stout prickles, dark green and rugose primary 
leaves with broad often orbicular leaflets, leafy flowering branch- 
lets, and suborbicular and incised unifoliate leaves of the 
prickly inflorescence. It is closely related to the plants herein 
described as Rubus flagellaris < frondosus and Rubus Baileyanus 
<frondosus, and some specimens afford the suggestion that the 
latter may be involved in its parentage. Its stronger forms, 
however, seem to reveal hints of both Rubus argutus and Rubus 
flagellaris, and I know not to what influence other than that of the 
latter its orbicular denticulate leaflets may be attributed. That 
