232 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves broad, not linear; pods 8-12 cm. long, 10-20 mm. thick. 

 Leaves thin, ovate or ovate-lanceolate, taper-pointed; corolla lobes pink, the 



hoods white 2. A. quadrifolia. 



Leaves rather stiff, oval, ovate, or obovate; corolla lobes white, the hoods purplish. 



9. A. variegata. 



Leaves scattered or opposite. 



LeaveB scattered; juice not milky. Corolla pale or dark orange; plants hairy. 



4. A. tuberosa. 

 Leaves mainly opposite; juice milky. 



Leaves heart-shaped, clasping, glabrous, wavy-margined. Corolla greenish pur- 

 ple or decidedly purplish 5. A. amplexicaulis. 



Leaves sessile or ehort-petioled, not clasping. 

 Stems usually much branched above. 



Plants glabrous or nearly so; leaves seldom over 2.5 cm. wide; petioles 4-10 



mm. long; corolla lobes and hoods rose-purple 10. A. incarnata. 



Plants soft-hairy throughout; larger leaves commonly over 2.5 cm. wide; 

 petioles 2-5 mm. long; corolla lobes and hoods pale pinkish. 



11. A. pulchra. 

 Stems normally simple. 

 Pods densely woolly, 2-3 cm. thick, usually warty with soft processes, but 

 occasionally smooth. Leaves downy beneath; corolla whitish to dull 



purple, often fading greenish yellow, the hoods darker 6. A. syriaca. 



Pods neither woolly nor warty, usually less than 2 cm. thick. 

 Leaves downy beneath. Corolla lobes and hoods dark purple. 



7. A. purpurascens. 

 Leaves glabrous beneath. 



Leaves sessile, long taper-pointed. Corolla lobes and hoods purplish red. 



8. A. rubra. 



Leaves petioled. 



Leaves taper-pointed, ovate; corolla lobes greenish purple, the hoods 



white or pink 3. A. phytolaccoides. 



Leaves oval, ovate, or obovate; corolla lobes white, the hoods purplish. 



9. A. variegata. 



1. Asclepias verticillata L. 



Rather dry open woods; occasional. July-Aug. Widely distributed in N. Amer. 



2. Asclepias quadrifolia Jacq. 



Rather uncommon on wooded hillsides near the Potomac, above Georgetown. 

 May-June. Eastern N. Amer. 



3. Asclepias phytolaccoides Pursh. 



Woodside, June, 1896 (II. W. Oldys). Eastern U. S. 



4. Asclepias tuberosa L. Butterfly-weed. Pleurisy-root. 

 Frequent in dry open places. June-Aug. Widely distributed in the U. S. (A. 



decumbens L.) 

 Used in medicine and cultivated as an ornamental plant. 



5. Asclepias amplexicaulis J. E. Smith. 



Common in open sandy places, especially on the Coastal Plain. May-July; fr. 

 Aug. Eastern U. S. (/I. obtusifolia Michx.) 



6. Asclepias syriaca L. Common milkweed. 

 Common in open moist ground, especially along highways and in pastures, often 



appearing as if an introduced weed. June-July. Eastern N. Amer. (A. cornuti 

 Decaisne.) 



7. Asclepias purpurascens L. Purple milkweed. 

 Thickets along the Potomac and Rock Creek; occasional. June. Eastern U. S. 



