942 ASCLEPIADACEAE 



Leaf-blades typically oval : umbels globose : pedicels 2 cm. long. 11. A. variegata. 

 Leaf-blades mainly elliptic or elliptic-lanceolate, tapering to each 



end : pedicels drooping, 5 cm. long. 12. A. exaltata. 



b. Leaf-blades ovate-lanceolate to linear, glabrous ; primary veins ascend- 

 ing, never conspicuously transverse, (see also A. exaltata). 

 Leaf-blades ovate-lanceolate or long-lanceolate, long-acuminate : co- 

 rolla purple-red. 13. A. rubra. 

 Leaf-blades lanceolate to oblong-linear, short-petioled : corolla pur- 

 plish : hoods orange, exceeding the anthers. 14. A. lanceolata. 

 Follicles erect on erect fruiting pedicels: primary veins of the leaf-blades 



never transversely ascending. 

 Leaf-blades broad, ovate to ovate-lanceolate, oblong-lanceolate or sometimes 



lanceolate. 



Some of the leaves whorled in 4's or 6's : flowers rose-pink. 15. A. quadrifolia. 



Leaves all opposite. 



Corolla and hoods rose-colored or rarely white. 



Plants glabrous throughout or nearly so : leaves oblong-lanceolate, 



in the variety elongated-linear. 16. A. incarnata. 



Plants hirsute-pubescent : leaves broader. 17. A. pulckra. 



Corolla red-purple : hoods bright orange : leaves oblong to oblong-lan- 

 ceolate. 18. A. Curassavica. 

 Corolla and hoods white, tinged with green or pink : flowers very small. 

 Leaf-blades oblong-lanceolate or lanceolate, tapering at each end, 



glabrous : seed destitute of coma. 19. A. perennis. 



Leaf-blades oval-oblong, broad at the petioled base. 20. A. Texana. 



Leaf-blades linear or filiform : flowers very small, white or greenish tinged. 

 Hoods each terminating in a horizontal or erect lobe : horns exserted. 

 Crown slender-stalked, the stalk less than 1 mm. thick : horn exceed- 

 ing the hood. 

 Leaf-blades filiform or linear-filiform. 



Stems typically solitary : leaves numerous, but not crowded. 21. A. verticillata. 

 Stems tufted : leaves contiguous or approximate, very numerous 



and crowded. 22. A. pumila. 



Leaf-blades linear. 23. A. nMorfe, 



Crown short-stalked, the stalk over 1 mm. thick : horn not exceeding 



the hood. 

 Umbel typically solitary, sessile : leaves many times longer than 



the internodes. 24. A. Michauxii. 



Umbels several, peduncled : leaves shorter than the internodes or 



less than twice their length. 25. A. viridula. 



Hoods notched or emarginate : horn included. 26. A. cinerea. 



B. Hoods erect, dilated above the anthers into a lobed or erose open or closed 

 lamina: anther-wings entire or notched at the middle or corniculate at the base. 

 Leaf-blades with ascending veins : umbels all lateral. 



Hoods 5 mm. high : horn single, arising from the apex of the hood. 27. A. Emoryi. 



Hoods 8 mm. high, very slender at the stalked base : horn with an acute 



dorsal accessory process. 28\ A. Lindheimeri. 



Leaf-blades with transversely spreading veins : horn arising from the base of 



the hood, exserted over the anthers. 29. A. obovata. 



1. Asclepias deciimbens L. Stems decumbent, 3-6 dm. long, hispid or hirsute- 

 pubescent, the ends ascending or erect : leaves various, the lower commonly alternate, the 

 upper opposite and often notably smaller ; blades oblong, obtuse at the apex, mostly nar- 

 rowed and often inequilateral and sometimes hastate at the base, usually revolute on the 

 margins, 3-19 cm. long : umbels several or numerous, many-flowered, racemose along the 

 branches, one usually in each of the upper axils, on peduncles 1-3 cm. long : pedicels 

 slender, somewhat pubescent, 1.5-3 cm. long: corolla lobes narrowly oblong, acutish, dark 

 or pinkish orange color, 7 mm. long : column distinct : hoods erect, linear, oblong, orange- 

 yellow, slightly longer than the subulate inflexed horn, the ventral margins entire or barely 

 lobed at the base : follicles 10-14 cm. long, slender-fusiform, hipsid-pubescent : seeds 7 mm. 

 long, glabrous, marked by fine broken diverging ridges : coma long and abundant. 



In dry fields, New York, Ohio and Illinois to North Carolina and Florida. Occurring also probably 

 elsewhere further north. Summer. BUTTERFLY WEED. PLEURISY-ROOT. 



2 . Asclepias tuberosa L. Stems solitary or several, hirsute or rough hirsute-pubes- 

 cent, commonly erect or ascending, 3-6 dm. high or more, simple or branched near the sum- 

 mit, very leafy, the milky sap scanty : leaves usually all alternate ; blades lanceolate-oblong, 

 sometimes lanceolate-linear, acute or more rarely obtuse at the apex, 3-9 dm. long, with 

 margins narrowly revolute : umbels cymose at the ends of the stems or branches, or on old 

 plants sometimes racemose, many-flowered: pedicels pubescent, 1-1.5 cm. long: corolla- 

 lobes narrowly oblong, obtuse, 6-8 mm. long, greenish or reddish orange : column distinct : 

 hoods erect, linear-oblong or linear-lanceolate, bright orange-color or rarely yellow, con- 

 siderably exceeding the anthers and slightly longer than the filiform exserted incurved 

 horn, the ventral margins entire or barely lobed and overlapping at the base : anther-wings 

 salient at the entire base : follicles 7-10 cm. long, minutely pubescent : seeds 7 mm. long, 

 glabrous, marked with fine diverging broken ridges : coma long and abundant. 



In dry fields, Maine to Ontario, Minnesota, Colorado, Florida, Texas and Arizona. Summer and 

 fall. BUTTERFLY WEED. PLEURISY-ROOT. 



