Jones: Flora of Illinois, 129. Asclepiadaceae 207 



woods, common. June-Aug. Butterfly-weed [/I. deciimbens L.} 



...A. tuber osa L. 



1. Flowers not orange or yellow; plants not hirsute; sap milky. 



2. Leaves narrowly linear, mostly in whorls of 4-6; flowers white; follicles 

 erect, glabrous, narrowly lanceoloid, 6-9 cm. long, on erect pedicels; 

 roadsides, or sandy soil in fields and open woods, common. June-Aug. 



Horsetail Milkweed A. verticillata L. 



2. Leaves not narrowly linear. 



3. Leaves sessile or clasping, opposite; plants glabrous, pale green, some- 

 what glaucous. 

 4. Follicles smooth; umbel solitary, terminal. 



5. Leaves elliptical, cordate-clasping, wavy-margined, obtuse, mucron- 

 nulate, 7-15 cm. long; corolla pale greenish purple, 8-9 mm. 



long; sandy soil along roads and in open woods. June-July 



A. amplexicaiilis Sm. 



5. Leaves lanceolate to ovate-lanceolate, sessile, flat, acute or obtusish, 

 3-7 cm. long, the margins minutely roughened; flowers greenish 



white; dry ground, rare. Peoria, Brendel; McDonald 



A. meadit Torr. 



4. Follicles somewhat echinate toward the apex with a few short blunt 

 processes, glabrous, 8-13 cm. long, ovoid or lanceoloid; umbels 

 terminal and lateral; leaves obtuse, mucronulate, elliptical, the 

 margins flat; prairie soil, or along roads, extending southw. to Ma- 

 coupin and Coles counties. July-Aug. Smooth Milkweed 



A. sullivantii Engelm. 



3. Leaves manifestly petioled. 



6. Leaves pubescent beneath; fruiting pedicels deflexed. 



7. Follicles tomentose, 2-3 cm. thick, warty with soft-spinulose subu- 

 late processes; flowers lavender and green; roadsides, fields, and 

 woods, common. June-Aug. Common Milkweed ....A. syriaca L. 

 7. Follicles smooth, less than 2 cm. thick. 



8. Corolla-lobes dark purple, 8-10 mm. long; hoods red or purple; 

 follicles 9-12 cm. long; leaves 10-20 cm. long; sandy soil, 

 along roads, and in open woods, local. June-July. Purple Milk- 

 weed A. purpurascens L. 



8. Corolla-lobes greenish white tinged with purple, 4-5 mm. long; 

 hoods yellowish; follicles 6-8 cm. long; leaves 5-8 cm. long; 

 open woods, rare. Cook Co., Babcock A. ovalifolia Dec. 



6. Leaves glabrous or nearly so. 



9. Fruiting pedicels erect; leaves lanceolate, acuminate; corolla-lobes 

 3-5 mm. long. 

 10. Flowers rose-purple, rarely whitish; leaves all opposite; moist 

 ground, roadsides, ditches, or in woods, common. July-Aug. 



Swamp Milkweed A. incarnata L. 



10. Flowers pink or white; leaves thin. 



11. Flowers pink; median leaves usually whorled; seeds with a 



