218 NORTH AMERICAN FLORA 
Pappus represented in both disk- and ray-flowers by a more 
or less developed crown or margin. 
Receptacle high, hemispheric or conic; achenes with 3-5 
ribs on the inner half and nerveless on the back; ligules 
white. 
Receptacle flat or slightly convex; achenes equally 3—10- 
angled or 3—10-ribbed. 
Achenes all 5-10-ribbed or 5-10-angled; bracts of the 
involucre more or less imbricate, the outer shorter; 
ligules in ours white. 
Achenes of the ray-flowers 3-angled; bracts of the 
involucre nearly equal; ligules yellow. 
Pappus at least in the disk-flowers wholly wanting. 
Achenes all 10-ribbed or 10-angled; ligules white. 
Achenes of the ray-flowers with 2 or 3 wing-angles; ligules 
yellow. 
Heads discoid or apparently so; pistillate ray-flowers, if present, 
without well-developed ligules. 
Marginal pistillate flowers, if present, with corollas; achenes 
not flattened. 
Anthers with ovate, mostly obtuse tips; heads solitary at 
the ends of the branches or in a corymbiform in- 
florescence. 
Heads discoid, homogamous, i. e., ray-flowers wholly 
wanting. 
Receptacle high, hemispheric or conic; involucral 
bracts subequal in 2-3 series; achenes 3—5-ribbed 
on the inner side and nerveless on the back; 
leaves pinnatifid into narrow divisions. 
Receptacle merely convex; involucral bracts in 4-5 
series, distinctly imbricate, the outer mruch 
shorter; achenes 10-ribbed; leaves broad, merely 
crenate or broadly lobed at the base, conspicu- 
ously punctate. 
Heads heterogamous; marginal pistillate flowers 
presert. 
Corollas of the marginal flowers oblique, with a 
somewhat developed ascending convex short 
ligule; pappus coroniform. 
Corollas of the marginal flowers cylindric or nearly 
so, 3- or 4-lobed, the limb not oblique; pappus 
wanting. 
Achenes subcylindric, neither utricular nor swell- 
ing in water, equally 5-10-angled; receptacle 
naked. 
Achenes obovoid, utricular, swelling and be- 
coming gelatinous in water; those of the disk 
5-angled, those of the rays 3-angled and 2- 
winged at the apex; receptacle pubescent. 
Anthers with subulate tips; heads racemose or racemose- 
paniculate, rarely solitary. 
Pappus present. 
Pappus of 5 subulate squamellae; heads solitary; 
receptacle naked. 
Pappus of a dentate or lacerate crown; heads pani- 
culate; receptacle pubescent. 
Pappus wanting. 
Corollas and achenes densely arachnoid-villous; 
spinescent shrubs. 
Corollas and achenes glabrous, glandular-granu- 
liferous, or the limb of the former rarely some- 
what pubescent; plant not spinescent. 
Marginal pistillate flowers without corollas; achenes strongly 
flattened, obcompressed. 
Heads peduncled; marginal flowers pedicelled; style de- 
ciduous or only the very base persistent. 
Heads sessile; marginal flowers sessile; style persistent, 
forming a spine-like beak. 
Achenes not hairy at the apex, with thin plane wings; 
disk-corollas cylindric, without differentiation be- 
tween tube and throat. 
Achenes villous at the apex, with thick corky wings; 
disk-corollas with a slender tube and elongate- 
funnelform throat. 
10. 
11. 
12s 
13. 
14. 
15: 
16. 
17. 
oF 
20. 
7A 
[VoLUuME 34 
. CHAMOMILLA. 
. MATRICARIA. 
. TANACETUM. 
. LEUCANTHEMUM. 
CHRYSANTHEMUM, 
. CHAMOMILLA. 
BALSAMITA. 
‘TANACETUM. 
SPHAEROMERIA. 
VESICARPA. 
CHAMARTEMISIA. 
CROSSOSTEPHIUM, 
PICROTHAMNUS. 
ARTEMISIA. 
LANCISIA. 
SoLiva. 
GyYMNOSTYLES. 
