

Compositaceae é 397 
P. Involucre-bracts almost flat, not enclosing the ray akenes; leaves narrowly 
linear, margins involute or revolute; heads 12-30 mm. wide; rays 3—6. 
BLEPHARIPAPPUS (p. 402) 
PP. Involucre-bracts boat-shaped, enclosing each an outer or ray akene. 
Q. Heads 12—25 mm. wide; rays 8—13; basal leaves often laciniately-lobed 
or -incised. LayIA (p. 404) 
QQ. Heads 4—12 mm. wide; rays 1—7; leaves all entire or nearly dentate. 
HEMIZONIA (p. 403) 
AA. Heads rayless, i. e., without ligulate flowers. 
R. Pappus none; heads few-flowered; flowers yellow or greenish, the staminate and 
pistillate often in separate heads; fruit often bur-like. 
S. Leaves broadly lanceolate or wider, often lobed or pinnatifid; heads staminate 
or pistillate or with both kinds of flowers. 
T.  Involucre neither tubercled nor spiny; fruit not a bur; staminate and pistil- 
late flowers in the same head; plant merely puberulent or scabrous; lower 
leaves opposite. Iva (p. 397) 
TT. Involucre of pistillate heads either tubercled or spiny, making fruit rough 
or bur-like; stammate and pistillate flowers in separate heads; plant either 
hairy or all the leaves alternate. 
U.  Involucre-bracts of the staminate heads united; fruit often not a bur but 
when so the bristles usually not hooked. 
V. Fruit with | whorl of prickles at the top, 1-seeded. 
AMBROSIA (p. 398) 
VV. Fruit with prickles in more than | whorl or scattered, |—4-seeded. 
FRANSERIA (p. 398) 
UU. Involucre-bracts of the staminate heads distinct; fruit a bur with 
20—100 usually hooked bristles. XANTHIUM (p. 398) 
SS. Leaves linear or linear-lanceolate, entire or remotely serrulate; heads with per- 
fect flowers only; involucre neither tubercled nor spiny. Mapia (p. 402) 
RR. Pappus of short teeth or barbed awns; heads many-flowered, all alike; flowers 
yellow or brown or purple, perfect; fruit not bur-like. 
W. Leaves all alternate; flowers purple or brown; pappus a crown of 2—4 scales. 
RUDBECKIA (p. 399) 
WW. Leaves opposite at least below; flowers yellow; pappus of 2—6 retrorsely- 
barbed awns. | _ BipENS (p. 401) 
IVA MARSH ELDER 
Puberulent or scabrous. Leaves opposite or the upper alternate, simple, somewhat 
3-veined from base. Heads rayless but with 2 forms of flowers, small, nodding, greenish, 
either solitary in the leaf-axils or else in spikes or racemes or panicles; involucre-bracts 
few, rounded. Marginal-flowers 1—6, pistillate, fertile: corolla none or tubular. Disk- 
flowers perfect, sterile, 5-lobed. Akenes flattish, obovoid, glabrous. Pappus none. 
(Named from Ajuga iva, a plant with a similar odor. ) 
A. Leaves oblong to obvoate, mostly entire, sessile; heads mostly solitary in the axils; 
involucre bracts about 5; perennial. E. 
I. axillaris Pursh (Poverty-weed) 
. AA. Leaves ovate to orbicular, coarsely serrate, long-petioled; heads in axillary spikes; 
involucre bracts about 10; annual. — E. 
I. xanthifolia Nutt. 
