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, filif(,)rm-linear, 2-6 cm. long, 1-3 

 mm. wide, the margins revolnte, 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 asor 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 tlie 

 base of the hood, elongated subulate-falcate, horizontally e.Kserted 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 cm. long. 



In dry and sterile soil, Canada to Nebraska, Florida and Texas. Spring to fall. 



22. Asclepias pimila (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 revolnte 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 nim. 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 cm. long, minutely puberulent. [A. verticillata var. pmnila 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, 1-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 Michauxii 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 kase and inflexed-exserted over 

 the anthers at the middle of the hood : anther-wings entire or sliglitly notched at the angled 

 and salient base : follicles slender-fusiform, erect on erect fruiting j^edicels, 8-14 cm. long, 

 6-7 mm. or 8 mm. wide, attenuate at each end, usually minutely ]iuberulent : seeds 7 mm. 

 long, about 5 mm. wide, with the margin conspicuously broad : coma 2.5 cm. long. 



In pine lands and on sand hills, South Carolina to Florida and Mississippi. Spring. 



25. Asclepias viridula 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- 



