GENUS i. 



MILKWEED FAMILY. 



19. Asclepias ovalifolia Dec. Oval-leaved 

 or Dwarf Milkweed. Fig. 3401. 



Asclepias ovalifolia Dec. in DC. Prodr. 8 : 567. 1844. 



Finely tomentose all over ; stem simple, usually 

 slender, erect, io'-2 high. Leaves oval, ovate, 

 oblong or ovate-lanceolate, acute or obtuse and 

 mucronulate at the apex, rounded or narrowed at 

 the base, 2'-$' long, 4'-ii' wide, short-petioled, 

 the upper surfaces becoming glabrate at maturity; 

 umbels solitary or few, several-many-flowered ; 

 peduncles short; corolla greenish-white or pur- 

 plish, its segments ovate-oblong, obtuse, 2" -3" 

 long ; column very short ; hoods oval-oblong, yel- 

 lowish, nearly twice as long as the anthers, bear- 

 ing a large acute tooth on each of the inner "mar- 

 gins ; horn subulate, incurved over the stigma ; 

 follicles ascending on the reflexed fruiting pedi- 

 cels, pubescent. 



In woods and on prairies, Illinois to North Dakota, 

 \Visconsin, Manitoba and Athabasca. June-July. 



20. Asclepias brachystephana Engelm. 

 Short-crowned Milkweed. Fig. 3402. 



Asclepias brachystephana Engelm. ; Torr. Bot. Mex. 

 Bound. Surv. 163. 1859. 



Puberulent when young, soon glabrate ; stems 

 clustered, often branched, spreading or ascend- 

 ing, 6' -i 2' long. Leaves mostly opposite, lanceo- 

 late or linear-lanceolate, thick, long-acuminate at 

 the apex, rounded, subcordate or narrowed at the 

 base, 2'-5' long, 2 "-6" wide, or the lowest shorter ; 

 petioles I "-4" long; umbels several, terminal and 

 axillary, few-flowered; peduncles short; pedicels 

 densely woolly, equalling or longer than the pe- 

 duncles; corolla greenish-purple, its segments 

 about 2" long; column very short or none; hoods 

 ovate, obtuse, shorter than the anthers, the short 

 erect-incurved horn slightly exserted; follicles 

 erect on the spreading or decurved fruiting pedi- 

 cels, downy or hoary, acuminate, 2'-$' long. 



In dry soil, Kansas (according to B. B. Smyth), 

 Wyoming to Texas, Arizona and Mexico. June-Aug. 



21. Asclepias perennis Walt. Thin-leaved 

 Milkweed. Fig. 3403. 



Asclepias perennis Walt. Fl. Car. 107. 1788. 



Puberulent above, glabrous below ; stem slen- 

 der, simple or branched, erect, i -3 high. Leaves 

 thin, opposite, lanceolate, oblong or ovate-lanceo- 

 late, slender-petioled, acuminate or acute at both 

 ends, 2'-6' long, \'-\' wide, nearly glabrous; um- 

 bels solitary or several and corymbose ; peduncles 

 i '-2' long; pedicels slender, i'-i' long; flowers 

 small, white; corolla-segments oblong, i"-2" 

 long; column about \" h ; gh ; hoods oval, erect, 

 entire, about as long as the anthers, shorter than 

 the subulate-filiform incurved horn ; follicles gla- 

 brous, erect on the nearly erect fruiting pedicels ; 

 seeds 5"-6" long, 3*"-4i ' wide, thin, usually with- 

 out coma. 



On river-shores and in wet places, North Carolina 

 to Indiana, Illinois and Missouri, south to Florida 

 and Texas. May-Aug. 



