ASCLEPIADACEAE 947 
umbels 15-20-flowered: pedicels 1 cm. long, stout, minutely pubescent: corolla-lobes 4 
mm. long, oblong, white : column very slender, tinged with purple: hoods erect, purple- 
veined, and obscurely sagittate-hastate on the back, the ventral margins entire, slightly 
infolded : horns broadish, prominently exserted over the anthers : follicles not seen. 
On plains or prairies, southern Texas. Summer, 
21. Asclepias verticillata L. Stems glabrous or minutely hirsute-pubescent, typically 
solitary from the short rootstock, simple or rarely branched, 3-5 dm. tall or more, commonly 
pubescent in lines: leaves numerous, in whorls of 3-6, but not crowded, or in depauper- 
ate forms the upper ones scattered; blades slender, filiform-linear, 2-6 cm. long, 1-3 
mm. wide, the margins revolute, the midvein lighter, conspicuous beneath: umbels 
terminal and lateral, 1.5-2.5 cm. in diameter, loosely few-flowered to many-flowered : 
corolla-lobes greenish white, 3-4 mm. long: column nearly 1 mm. high: hoods erect or 
erect-spreading, white, turning yellowish in drying, broadly oblong, as high as or slightly 
shorter than the anthers, truncate at the summit as well as at the hastate-sagittate base : 
ventral margins auriculate-involute at about the middle: horn rather flat, arising from the 
base of the hood, elongated subulate-falcate, horizontally exserted over the anthers, usually 
much exceeding the hood : anther-wings slender and narrow, entire or minutely notched 
at the angled and salient base : follicles erect on erect fruiting pedicels, very slender, 7-10 
cm. long, attenuated at each end, glabrous or minutely puberulous : seeds 7 mm. long, thin, 
pale brown, minutely pitted under a lens: coma 3 em. long. 
In dry and sterile soil, Canada to Nebraska, Florida and Texas. Spring to fall. 
22. Asclepias pumila (A. Gray) Vail. Stems glabrous or nearly so, tufted, 1-25. 
dm. high, simple or rarely branched : leaves contiguous or approximate, very numerous 
and crowded, 3.5 cm. long ; blades filiform-linear, the revolute margins glabrous or minutely 
scabrous-pubescent : umbels 2-several, few-flowered, short-peduncled, solitary or cymose at 
the summit of the stem: corolla greenish white; lobes oblong, 4-5 mm. long: hoods 
arising from the summit of the short column, oblong, erect, entire, equalling the 
anthers, shorter than the slender incurved horn: follicles erect on erect fruiting pedicels, 
narrowly fusiform, 3-5 em. long, minutely puberulent. [A. verticillata var. pumila A. 
Gray. ] 
On dry plains, South Dakota to Colorado, Arkansas and New Mexico. Summer. 
23. Asclepias linearis Scheele. Stems minutely pubescent, terete, angulate above, 
2-5 dm. high, simple or branched near the base, minutely pubescent, commonly in lines 
above: leaf-blades glabrous, narrowly linear, 4-8 cm. long or 10 cm. long, acute, gla- 
brous or with few scattered hairs, coriaceous, l-nerved, the veins obsolete, the margins 
revolute or plain: umbels 3-8, all lateral, 1.5-2.5 cm. in diameter, few- to several-flowered: 
column slender, conspicuous: corolla-lobes greenish white, about 4 mm. long, elliptical- 
oblong, acutish : hoods erect-spreading, broadly truncate at the summit, truncate at the 
hastate-sagittate obscurely clawed base, the ventral margins with rounded angles or lobes at 
the middle, somewhat involute: horn flat, arising from the keel of the hood near its base 
within, arcuate, horizontally long-exserted over the anthers, often dorsally angled at about 
the middle: anther-wings very slender, minutely notched at the angled base: follicles not 
seen. : 
In damp clay soil, southern Texas. Summer and fall. 
24. Asclepias Michaüxii Decne. Stems minutely puberulent, often clustered, 2-3 
dm. high from a stout ligneous fusiform rootstock, ascending or decumbent : leaves numer- 
ous, opposite, or some of them scattered ; blades linear or narrowly linear, 4-9 dm. long, 
scabrous or minutely scabrate, the margins sometimes becoming revolute: umbels typically 
solitary or rarely 2, sessile, 1-3: corolla greenish, tinged with dull purple on the outside ; 
lobes oval, 5 mm. long: column distinct : hoods erect-spreading, orange-color or yellowish, 
with apparently a purplish keel or mid-vein, ovate, entire, surpassing the anthers: ven- 
tral margins obscurely lobed : horn flat, inserted above the base and inflexed-exserted over 
the anthers at the middle of the hood : anther-wings entire or slightly notched at the angled 
and salient base : follicles slender-fusiform, erect on erect fruiting pedicels, 8-14 em. long, 
6-7 mm. or 8 mm. wide, attenuate at each end, usually minutely puberulent: seeds 7 mm. 
long, about 5 mm. wide, with the margin conspicuously broad : coma 2.5 em. long. 
In pine lands and on sand hills, South Carolina to Florida and Mississippi. Spring. 
25. Asclepias virídula Chapm. Stems nearly glabrous, 3-6 dm. high, sometimes 
pubescent in lines, very slender: leaves opposite; blades narrowly linear, 1-3 mm. wide, 
the margins sometimes revolute: umbels several, peduncled, 1-4-flowered : corolla-lobes 
greenish, oblong, 3-4 mm. long : hoods oblong, surpassing the anthers, the ventral mar- 
