Compositae. 953 
V. Heliantheae. 
Capitula heterogamous, radiate or rarely discoid, 
ray florets female fertile or neuter, disk-florets 
bisexual fertile or sterile; or capitula homo- 
gamous discoid unisexual or with all the florets 
bisexual. Involucral bracts various. Receptacle 
paleaceous or rarely on the disk, under the 
sterile florets, naked. Corolla of the bisexual 
florets tubular, regular 4—5 cleft. Anthers 
appendaged at the apex, at the base entire 
obtusely or scarcely tailed. Style-branches of 
the bisexual florets truneate or appendaged. 
Achenes various, usually compressed or angular; 
pappus aristate or shortly paleaceous or wan- 
ting. — Leaves at least the lower ones, usually 
opposite. Flowers usually yellow. 
a) Ambrosinae. — Heads small and discoid; 
only the female flower fertile; these few 
and with no corolla, or a rudimentary one 
in the form of a short tube surrounding 
the base of the style. Bisexual-sterile or 
male flowers with campanulate limb to the 
corolla; anthers slightly cohering or nearly 
distinct, their inflexed tips often mucronulate 
or cuspidate; the abortive style entire, with 
truncate apex tipped with a minute radiate 
tuft or brush. Pappus none. Achenes 
usually obovate and thick. 
1. Involucre of the male capitula gamo- ' 
phyllous; female capitula 1-flowered. . 27. Ambrosia. 
2. Incolucre of the male capitula with three 
bracts. Female capitula 2-flowered . . 28. Xanthium. 
b) Zinnieae. — Heads always heterogamous 
with ligulate somewhat rigid corollas; tube 
very short and small, persistent on the ripe 
fruit. Disk-florets bisexual, mostly fertil. 
Leaves opposite, rarely whorled . ... . 29. Zinnia. 
c) Verbesininae. — Heads radiate the rays 
either neutral or female, or else rayless; 
the disk-flowers perfect and fertile, each 
subtended by a chaff of the receptacle. 
Achenes thick and 8—4-angular; or those of 
the disk laterally compressed (i. e. contrary 
