PART 6, 1918] ROSACEAE 497 
18. Rosa dasistema Raf. Ann. Gén. Sci. Phys. 5: 219. 1820. 
Stem terete, armed with small curved prickles 3-5 mm. long; branches spreading; stipules 
narrow, 1 cm. long or less, glabrous or slightly pubescent, the free portion short, lanceolate or 
subulate, spreading; petioles and rachis sparingly hairy, sparingly prickly, sparingly pubes- 
cent; leaflets 5, rarely 7, elliptic, glabrous on both sides or somewhat pubescent on the veins 
beneath, 2—4 cm. long, finely crenate-serrate, obtuse or acute at each end; flowers solitary or 
two together; pedicels short, usually about ‘1 cm. long, glandular-hispid; hypanthium more or 
less pyriform or ellipsoid, acute at the base, glandular-hispid, about 8 mm. thick in fruit; 
sepals linear-lanceolate, caudate-acuminate, 12-15 mm. long, glandular-hispid without, 
tomentose within, after anthesis spreading and soon deciduous; petals 1.5-2 cm. long; styles 
numerous, not exserted, distinct; achenes inserted in the bottom of the hypanthium. 
TyPE LocaLity: Ohio and Indiana. | ; 
DISTRIBUTION: Swamps of West Virginia, Ohio, Indiana, and Missouri. 
Rosa dasistema X virginiana. This has the leaf form and serration of R. dasistema, and the 
hypanthium is acute at the base, but the plant is stouter, the leaves larger and more shining, and 
the prickles very stout and straight or nearly so. Wet places, Butler County, Missouri, August 2, 
1892, H. Eggert. 
19. Rosa gemella Willd. Enum. 544. 1809. 
Rosa cinnamomea gemella Seringe, in DC. Prodr. 2: 605. 1825. 
Stem low, 3-10 dm. high, often reddish, terete, rarely bristly, armed with short curved 
prickles 4-5 mm. long; stipules narrow, or the upper dilated, about 1.5 cm. long, adnate, 
glabrous or nearly so, often glandular-dentate; petiole and rachis glabrous, sometimes glandu- 
lar-hispid; free portion of the petiole 3-8 mm. long; leaflets 5—7, elliptic, oval, or obovate, 
1.5—3 cm. long, acute at the base, usually obtuse or rounded at the apex, finely serrate, glabrous 
on both sides or slightly pubescent on the veins beneath; flowers 1-4, corymbose; pedicels 
1-3 em. long, glandular-hispid; hypanthium globose, glandular-hispid, in fruit 10-12 cm. broad; 
sepals lanceolate, caudate-acuminate, glandular-hispid on the back, tomentose within, entire 
or with a few subulate lobes, reflexed after anthesis and soon deciduous; petals obcordate, 
about 2 cm. long; styles distinct, persistent, not exserted; achenes in the bottom of the hy- 
panthium. 
TYPE LOCALITY: North America. 
DISTRIBUTION: Massachusetts to southern New York. 
20. Rosa nanella Rydberg, sp. nov. 
Stem low, 1-3 dm. high, dark reddish-brown, glabrous, terete, armed with short some- 
what curved prickles, which are 3-5 mm. long, somewhat curved; young shoots somewhat 
bristly; floral branches short, ascending; stipules adnate to the petioles, 1-1.5 cm. long, glabrous 
or slightly pubescent, sparingly glandular-ciliate, the free portion lanceolate, ascending; petiole 
and rachis glabrous or nearly so; leaflets 5—7, rather shining, glabrous on both sides, oblanceolate 
or lance-elliptic, 1-2 cm. long, acute, serrate, with simple teeth; flowers usually solitary; 
pedicels 1-1.5 cm. long, glandular-hispid; hypanthium subglobose, somewhat glandular-hispid, 
in fruit 7-10 mm. in diameter; sepals spreading, glandular-hispid, soon deciduous; styles 
distinct, numerous, not exserted, persistent; achenes attached in the bottom of the hypanthium. 
Type collected September 29, 1915, at Chappaquiddick Island, Massachusetts, E. P. Bicknell 
(herb. N. Y. Bot. Gard.). 
DISTRIBUTION: Sand-dunes, from southern Massachusetts to New Jersey. 
Rosa Bicknellii X nanella. See under R. Bicknellii. 
21. Rosa obtusiuscula Rydberg, sp. nov. 
Stem slender, dark-brown, about 1 m. high, practically unarmed, branched; stipules ad- 
nate, narrow, about 1 cm. long, sparingly pubescent, the free portion lanceolate, more or less 
toothed; petiole and rachis sparingly pubescent, unarmed; leaflets 5 or 7, elliptic, rounded 
at the apex, crenate, dark-green, glabrous on both sides or sparingly pubescent beneath, 1—4 
cm. long; flowers 1—4 together; pedicels short, rarely over 1 cm. long, sparingly glandular; 
hypanthium depressed-globose, sparingly glandular-hispid, in fruit 8-10 mm. thick; sepals 
