ie 
_ AND GENERA OF PLANTS. 369 
Has. With the above, which it closely resembles, but is a more slender plant, with smaller 
flowers; terminal leaflet largest, the lateral often small. Achenia a litile bristly, sometimes with 
omy, one awn, or even without any, in the same capitulum with most of the others possessing awns. 
Bidens * angustifolia; very smooth and herbaceous; leaves pseudopinnate, 
in two or three pairs; segments narrow-lanceolate, acuminate, serrate, the low- 
est leaflet sometimes divided; panicle trichotomous, contracted; sepals nearly 
equal; rays about five, longer than the disk; achenium ciliate with erect bris- 
tles, two-awned, the awns retrorse at the summit. 
Has. With the above, from which it differs in the narrow and pinnated leaves; the fruit has, 
also, longer awns, and the pedicels are short. ‘The stem twelve to eighteen inches high, Awns 
of the achenium sometimes unequal, or of different lengths in the same capitulum. 
+ Bivens proper. 
Bidens *harsuta; herbaceous, nnd more or less hirsutely pubescent; stem 
quadrangular, grooved, trichotomous; leaves pseudopinnate, in two or hre ; 
pairs, the uppermost sometimes ternate, segments lanceolate, acuminate, in- 
cisely serrate, lateral divisions with the base obliquely attenuated; rays none; 
involucellum eight-parted, shorter than the involucrum; achenium subquad- 
rangular, with a wide, circular, basal areole, the angles hirsute or scabrous 
above; awns three, unequal, strongly retrorse barbellate. 
Has. In Atooi. Two to three feet high, with a thick, hirsute, quadrangular stem, oppositely 
branched. Leaves much like those of 2grimonia Eupatoria; hence, I suspect it is closely allied 
to B. Wallichit. It is, however, destitute of rays. Outer involucrum with the segments connected 
together at the base; the inner, also, about eight-leaved. Achenium linear, straight, smooth, except 
the upper edges of the angles, which are ciliate with tubercular, short bristles; awns about three, a 
third the length of the fruit, with strong, barbellate bristles their whole length. Hairs of the stem 
‘broad, flat, membranaceous and acuminate. Branches of the stigma with long, acuminated, slender 
points. z 
: * MICRODONTA. 
Capitulum many-flowered, heterogamous; rays feminine in a single series, 
(about five,) many-nerved. Discal florets hermaphrodite, tubular-campanu- 
late, five-toothed, the tube short and slender. Receptacle flat, paleaceous; 
palea oblong, similar with the inner involucrum. Involucrum double, the 
outer six-leaved, foliaceous, the inner about five-leaved, discoloured, some- 
what scarious. Achenia flatly sca those of the ray elliptic, mi- 
vi.—4 s 
