30 ASCLEPIADACEAE. Vor. III. 
16. Asclepias syriaca L. Common Milk- 
weed. Silkweed. Fig. 3398. 
Asclepias syriaca L. Sp. Pl. 214. 1753. 
Asclepias Cornuti Dec. in DC. Prodr. 8: 564. 1844. 
Stem stout, usually simple, 3°-5° high, finely 
pubescent at least above. Leaves oblong, oval or 
ovate, finely and densely pubescent beneath, soon 
glabrous above, acute or obtuse and cuspidate at 
the apex, obtuse, narrowed or subcordate at 
the base, 4’-9’ long, 2’-44’ wide, the primary nerves 
wide-spreading; petioles stout, 3-8” long; umbels 
several or numerous; peduncles pubescent or tomen= 
tose, 12-34’ long; pedicels 1-2’ long; corolla green- 
purple or greenish-white, its segments oblong-lan- 
ceolate, 3’—4’”" long; column short and thick, the 
hoods ovate-lanceolate with a tooth on each side, 
longer than the anthers and the incurved horn; fol- 
licles 3’-5’ long, erect on recurved pedicels, tomen- 
tose and covered with short soft processes. 
In fields and waste’ places, New Brunswick to Sas- 
katchewan, North Carolina and Kansas. Leaves rarely 
: lanceolate. Silky swallow-wort. Virginia silk. Wild 
~ cotton. June-Aug. 
Asclepias kansana Vail, of Kansas, differs by erect-spreading hoods of the corolla and more 
densely tomentose follicles. 
17. Asclepias specidsa Torr. Showy Milk- 
weed. Fig. 3399. 
Asclepias speciosa Torr. Ann, Lyc. N. Y. 2: 218. 1826. 
A, Douglasit Hook. Fl, Bor. Am. 2: 53. pl. 152. 1834. 
White-tomentose or canescent all over, or gla- 
brate below, pale; stem simple, stout, 1°-23° high. 
Leaves thick, broadly ovate or oval, obtuse and cus- 
pidate or acute at the apex, subcordate, rounded or 
narrowed at the base, petioled, 3’-8’ long, 2’-4’ wide; 
peduncles 1’-3’ long; umbels several or rarely soli- 
tary, many-flowered; pedicels stout, 9-18” long; 
corolla purple-green, its segments oblong or ovate- 
oblong, 4’-6” long, tomentose on the outer face; 
column very short or none; hoods lanceolate, 5’’-7” 
long, obtusish, expanded and with 2 blunt teeth be- 
low, the apex ligulate, 5-7 times as long as the 
anthers; horn short, inflexed; follicles erect or 
spreading on the recurved fruiting pedicels, 3’-4’ 
long, densely woolly and covered with soft spinose 
processes. 
In moist soil, Minnesota to British Columbia, south 
to Kansas, Utah and California. May-July. 
18. Asclepias arenaria Torr. Sand Milk- 
weed. Fig. 3400. 
A, arenaria Torr. Bot. Mex. Bound, Surv. 162, 1859, 
Densely tomentose-canescent all over, stems 
simple, ascending or erect, stout, 1°-2° high. 
Leaves obovate or oval, wavy-margined, thick, 
obtuse or retuse and cuspidate at the apex, trun- 
cate, subcordate, obtuse, or rarely some of them 
narrowed at the base, 2-4’ long, 14’-3’ wide, the 
angle of the primary nervation broad; umbels 
densely many-flowered, short-peduncled or ses- 
sile; corolla greenish-white, its segments oval- 
oblong, 4-5” long; column 1’-2” high; hoods 
oblong, truncate at each end, oblique at the apex, 
longer than the anthers, with a broad tooth on 
each side within; horn semi-lunate with an ab- 
tuptly incurved subulate apex; follicles puberu- 
lent, 4’-5’ long, erect on the decurved fruiting 
pedicels. 
On sand-bars and hills along rivers, Nebraska and 
Colorado to Mexico and New Mexico. June-Sept. 
