Bidens. | XLII. COMPOSITZ. 237 
flowers. Involucres of 2 or 3 rows of bracts, the outer ones often longer 
and leafy. Florets either all tubular, or the onter ones ligulate and radi- 
ating. Receptacle with chaffy scales between the florets. Achenes flat- 
tened, crowned by 2 or 3 (very rarely 4 or 5) short, stiff bristles or awns, 
which are rough, with minute deflexed prickles. 
A genus not very numerous in species, but diffused over the whole 
surface of the globe, some species being among the commonest tropical 
weeds, while others extend into the Arctic Circle. 
Leavesundivided . apes So VA ER ero ot. j,, lx Be ceentas 
Leaves deeply cut into 3 to 5 ‘segments - ; : . 2 B. tripartita. 
1, B.cernua, Linn. (fig. 519). Nodding ae Bur-Marigold.-— 
A rather stout, erect annual, 1 to 2 feet high, with spreading branches. 
Leaves lanceolate and serrate, but not divided. Flower-heads drooping, on 
terminal peduncles, from half an inch to an inch diameter; the florets 
usually all tubular, but occasionally a few of the outer ones become ligu- 
late. Inner bracts of the involucre broad, and often shining, and yellow 
on their edges ; outer ones more leafy, and often much longer, and spread- 
ing. Awns of ‘the achenes 2 or 3, very rarely 4. 
In wet ditches and marshes, throughout the temperate and northern 
regions of Europe, Asia, and America. Common in England and southern 
Scotland. #7. summer and autumn. 
2, B. tripartita, Linn. (fig. 520). Three-cleft Bidens.—-Only differs 
from B. cernua in the leaves, which are deeply cut into 3 or 5 lanceolate 
segments, and in the flower-heads rather less drooping. 
Its geographical range and stations are the same as those of B. cernua, 
but it appears to-be rather less common in Britain. FV. summer and 
autumn, 
Se tee 
XII. CHRYSANTHEMUM. CHRYSANTHEMUM. 
Annual or perennial herbs (or, in some exotic species, shrubs), with 
alternate toothed or variously dissected leaves, and radiating flower-heads, 
solitary on terminal peduncles, or in corymbs. Involucres hemispherical, 
with a few rows of imbricate bracts, more or less scarious on the edges. 
Receptacle flat or convex, without scales. Achenes angular or striate, 
without any pappus, but sometimes crowned with a minute raised border. 
Style nearly that of Senecio. 
A considerable genus, extending over Europe, northern and central Asia, 
and northern Africa. It has been divided by modern botanists into a 
number of small genera, founded upon minute, almost microscopical 
characters, having little relation to general habit. Among them Pyrethrum 
has been the most generally adopted, although botanists are but little 
agreed as to the characters or species which should be assigned to it. 
Ray yellow. 
Ray white. ‘ 
Leaves toothed only . ‘ ‘ ‘ ‘ e 4 » 1. C. Leucanthemum, 
‘Leaves pinnate. 
Flower-heads in corymbs. Segments of the leaves 
pinnatifid and toothed . ‘ : : . 3. O. Parthenium, 
Flower-heads on terminal peduncles. Leaves 2 or 3 
times pinnate ; with narrow linear or filiformlobes 4. Matricaria inodore. 
The old yellow and white Chrysanthemums of our cottage gardens belong 
° f » 2 C. segetum, 
