ion. ASCLEPIADACEAE 183 



2. Trachelospermum Lemaire 



T. difformc (Walt.) A.Gray. Moist woods and along streams, 

 southern 111., rare. June-July. 



3. Apocynum L. — Dogbane 



1. Corolla 2-3 times as long as the calyx, pink or pink-striped. 



2. Corolla 6-9 mm long, pink, its lobes soon recurved; leaves 

 drooping or spreading; roadsides and open woods, common. 

 June-Aug. Spreading Dogbane A. androsaemijoliiim L. 



2. Corolla 4-7 nmi long, its lobes not recurved; leaves ascending; 



open woods, occasional; Peoria, McDojiald; Chase. Probably 



hybrids of A. androsaemijolium and A. cannahinum 



A. medium Greene 



1. Corolla 2.5-4 mm long, less than twice the length of the calyx, its 

 lobes shorter than the tube; leaves ascending, glabrous or pubes- 

 cent. 



3. Leaves of main stem short-petioled, elliptical, acute at apex, 



narrowed at base; corolla nearly white; follicles 12-20 cm 

 long, curved; coma of seed 2-3 cm long; roadsides, fields, 



open woods, common. June-Aug. [A. pubescens R.Br.] 



A. canjiabiniim L. 



3. Leaves of main stem subsessile or sessile, oval or ovate, obtuse or 

 acutish, the lower rounded, truncate or subcordate and often 

 clasping at base; corolla greenish white; follicles 4-10 cm 

 long, nearly straight; coma 8-18 mm long; roadsides and 

 fields, common throughout 111. June-Aug. [A. hypericifolium 

 Ait.] -- A. sibiricum Jacq. 



4. Vinca L. — Periwinkle 

 V. minor L. Running-myrtle. Roadsides, woods, cemeteries; nat. 

 from Eur. May-June. 



100. Asclepiadaceae Lindl. — Milkweed Family 



I. Stem erect or decumbent, not twining. 



2. Corolla-lobes reflexed 1. Asclepias 



1. Corolla-lobes erect-spreading; hoods prominently crested within 



2. Asclepiodora 



1. Stem twining. 



3. Leaves cordate; corolla-lobes erect. 



4. Corolla-lobes 5-6 mm long; pollinia pendulous; corona of 5 lanceolate 



erect segments 3. Ampelamus 



4. Corolla-lobes 8-12 mm long; pollinia horizontal; corona a disk or cup 



4. Gonolobus 



3. Leaves not cordate; corolla rotate, the lobes triangular-ovate, about 1 

 mm long; pollinia pendulous 5. Cynanchum 



1 . Asclepias L. — Milkweed 

 1 . Hoods of the crown each with a small incurved horn within. 

 2. Flowers orange or yellow; plants hirsute; sap watery; umbels 



