1316 CICHORIACEAE 
Pappus bright white. 
Leaf-blades spiny-toothed and often spiny along the midrib beneath : corollas yellow. 
Involucres 6-12-flowered. 1. L. virosa. 
Involucres 12-20-flowered. 
Involucres over 1.5 em. high : beak fully as long as the body of theachene. 2. L. Ludoviciana. 
Involucres less than 1.5 em. high: beak shorter than the body oftheachene. 3. L. sagittifolia. 
Leaf-blades without spines on the margins or midribs. 
Achenes thin, each prolonged into a slender beak. 
Involucre of 2 sets of bracts ; outer very short ; inner much longer: corol- 
las yellow to reddish, except sometimes in No. 6. 
Leaf-blades, at least some of them, pinnatifid. 
Leaves glabrous. 4. L. Canadensis. 
Leaves hirsute, at least their midribs. 
Lower leaf-blades all pinnatifid : beak of achene fully as long as 
the body. 5. L. hirsuta. 
Lower leaf-blades usually both entire and pinnatifid: beak of 
achene much shorter than the body. 6. L. graminifolia, 
Leaf-blades entire or merely toothed. 3. L. sagittifolia. 
Involuere with the outer and inner bracts connected by intermediate 
series: corollas blue. 7. L. pulchella. 
Achenes thick, beakless, sometimes contracted into a neck. 
Leaf-blades toothed : achene-body not narrowed into a neck. 8. L. villosa. 
Leaf-blades pinnatifid : achene-body narrowed into a slender neck. 9. L. Floridana. 
Pappus brown. 10. L. spicata. 
1l. Lactuca virósa L. Biennial, bright green, glaucous. Stems erect, 6-20 dm. 
tall, rigid, glabrous at least above the more or less hirsute base, paniculate above: leaves 
numerous ; blades oblong to oblong-lanceolate, or oblanceolate, 1-3 dm. long or shorter 
above, denticulate, and spinulose beneath, sessile and clasping : heads 6-12-flowered, 4-8 
mm. broad: involucre 10-13 mm. high; inner bracts 3 longer than the outer, narrowly 
linear, green : ligules yellow : achenes ribbed, thick-margined, the body fully 3 mm. long, 
sometimes surpassed in length by the slender beak. 
In waste places, fields and thickets; New York to Kansas, south to Georgia and Tennessee. 
Summer and fall. 
2. Lactuca Ludoviciàna (Nutt.) DC. Biennial, glabrous. Stems erect, 4-15 dm. 
tall paniculately branched above: leaves numerous; blades oblong-oblanceolate to ob- 
long or oblong-lanceolate, 5-20 cm. long, acute or short-acuminate, sinuate-lobed or 
pinnatifid, spinulose along the margins as well as the midnerve beneath, clasping: pedun- 
cles with few scales: heads in close or open panicles: involucres 16-20 mm. high; 
inner bracts linear-lanceolate, scarious-margined : ligules yellow : achenes brown or black, 
the body obovate or oval, 4 mm..long, 3-ribbed, the beak fully as long as the body. 
On plains and prairies, Minnesota to North Dakota, Arkansas and Texas. Summer and fall. 
3. Lactuca sagittifdlia Ell. Biennial, glabrous. Stems erect, 1-3 m. tall, panic- 
ulate above: leaf-blades spatulate, oblanceolate to oblong-elliptie, or lanceolate, 1-3 dm. 
long, acute or somewhat acuminate, irregularly dentate, narrowed at the base but sessile 
and partly clasping : peduncles more or less scaly : involucres 10-20 mm. high ; inner bracts 
linear to linear-lanceolate: ligules yellow or reddish: achenes 5 mm. long, not wing-mar- 
gined, strongly ribbed, the body longer than the beak. 
On banks and in dry soil, New Brunswick to Ontario, Nebraska and Georgia. Summer and fall. 
4. Lactuca Canadénsis L. Biennial, glabrous. Stems erect, 1-3 m. tall, panicu- 
late above, often mottled : leaf-blades various, those of basal-leaves spatulate or oblong, 
dentate or pinnatifid, sometimes shorter than the petioles, those of stem-leaves 1-3 dm. 
long, sinuate-pinnatifid, the edges entire or irregularly toothed : peduncles often with small 
scales : involucres 10-12 mm. high; bracts ovate-lanceolate to linear-lanceolate : ligules 
yellow : achenes oval-oblong, 3 mm. long, the beak fully as long as the body. 
In open ground, Nova Scotia to Saskatchewan, Florida and Louisiana. Summer and fall. 
5. Lactuca hirsüta Muhl. Biennial, hirsute or rarely glabrate. Stems erect, 6-12 
dm. tall, paniculate above : leaf-blades oblanceolate to oblong in outline, sinuate-pinnatine, 
1-2 dm. long, sometimes hirsute only near the base ; segments more or less angulately 
toothed : peduncles naked or nearly so: involucres 12-15 mm. long, often purplish ; bracts 
lanceolate to narrowly linear, the inner scarious-margined: ligules purplish yellow to 
white : achenes oblong or elliptic, 3-5 mm. long, the body shorter than the beak. 
In dry soil, Maine to Ontario and Minnesota, south to Alabama and Texas. Summer and fall. 
6. Lactuca graminifdlia Michx. Biennial or perennial, glabrous or nearly 80; 
glaucescent. Stems erect, 6-15 dm. tall, paniculately branched above: leaf-blades elon- 
gated-linear or narrowly linear-lanceolate, 10-40 cm. long, entire or with a few spreading 
or deflexed lobes; both the entire and pinnatifid types often on the same plant : peduncles 
often with minute scales: involucres 12-15 mm. high; bracts linear-lanceolate to ]anceo- 
late, the inner scarious-margined : ligules purple, blue or rarely white or yellowish : achenes 
elliptic or elliptic-oblong, 4-4.5 mm. long, the beak much shorter than the body. 
In fields or woods, South Carolina to Florida and. Texas. Spring to fall. 
