ASCLEPIADAOEAE (MILKWEED FAMILY) 663 



or sparingly pubescent beneath, those of the chief axis narrowed, at base to distinct 

 petioles (2-7 mm. long), those of the branches often subsessUe; central cyme 

 flowering first ; flowers erect ; calyx glabrous, its lobes about equaling the coruUa- 

 tube. — Gravelly or sandy soil, mostly near streams; on beaches becoming 

 dwarfed and diffuse, with smaller and narrower leaves {A. album Greene). 

 June-Aug. Varying greatly, the most recognizable extremes being 



Var. pubfiscens (li. Br.) DC. Calyx and pedicels pubescent ; leaves white- 

 pubescent beneath. {A. pubescens R. Br.) — R. I. to Ont., la., and southw. 



Var. nemorjlle (G. y. Miller) Fernald. Leaves mostly spreading or drooping 

 on elongate (1-1.6 cm. long) slender petioles. {A. nemorale G. S. Miller.) — 

 Open woods, Fairfax Co., Va. 



Var. hypericifblium (Ait.) Gray. Principal leaves sessile or subsessile, 

 rounded or subcordate at base. {A. hyperieifolium Ait.) — Que. to Sask. and 

 B. C, s. to w. Me., centr. N. Y., O., Kan., Col., and Cal. ; chiefly westw. 



ASCLEPIAdACEAE (Milkweed Family) 



Plants with milky juice, and opposite or whorled (rarely scattered) entire 

 leaves ; the follicular pods, seeds, anthers (connected loith the stigma), sensible 

 properties, etc., as in the preceding family, from which they differ in the commonly 

 valvule corolla, and in the singular connection of the anthers with the stigma, 

 the cohesion of the pollen into wax-like or granular masses (poUinia), etc., as 

 explained under the typical genus Asclepias. 



Tribe I. CYNANCHEAE. Anthers tipped with an infiexe^ or sometimes erect scarious mem- 

 brane, the cells lower than the top of the stigma ; polUnia suspended. 

 * Stems erect or merely decumbent, 



1. Asclepiodora. Corolla rotate, merely spreading:. Crown of 5 hooded fleshy bodies, with a 



salient crest in each. Leaves alternate. 



2. Asclepias. Corolla reflexed, deeply 5-parted. Crown as In no. 1, but with an incurved horn 



rising from the cavity of each hood. Leaves usually opposite. 



3. Acerates. Corolla reflexed or merely spreading. Crown as In no. 1, but with neither crest 



nor horn inside. Leaves mainly alternate. 



* * Stems twining ; leaves mostly opposite, 



4. Gonolobus. Corolla erect. Crown of 5 membranaceous flat bodies, terminated by a 2-clefl 



tail or awn. 



5. Cynanchum. Corolla rotate, spreading. Crown a fleshy 5-10-lobed ring or disk. 



Tribe 11. VnTCETOXfCEAE. Anthers with short if any scarious tip, borne on the margin of 

 or close under the dislc of the stigma ; pollinia horizontal. 



6. Vincetoxicum. Corolla rotate. Crown a wavy-lohed fleshy ring. Stems twining, 



1. ASCLEPIODdRA Gray 



Resembling Asclepias ; but the corolla-lobes ascending or spreading, and the 

 hoods destitute of a horn, widely spreading and somewhat incurved, slipper- 

 shaped and laterally compressed, the cavity divided at the apex by a crest-like 

 partition. — Umbels solitary and terminal or corymbed, loosely-flowered, I'olli- 

 cles ovoid, often somewhat murioate with soft spinous projections. ("Ao-KXijirKis, 

 and SSipoi' or Swped, the gift of Aesculapius.) 



1. A. viridis (Walt.) Gray. Almost glabrous; stems 3-7 dm. high; leaveti 

 alternate, short-petioled, ovate-oblong to lanceolate, 3-13 cm. wide; u-^bels 

 several in a cluster, short-peduncled ; flowers large (2-3 cm. broad), green, 

 with a purplish crown. — Prairies, 111. to Tex. and S. C. May, June. 



2. ASCL:^PIAS [Tourn.] L. Milkweed. Silkweed 



Calyx persistent; divisions small, reflexed. Corolla.deeply 6-parted ; divisions 

 valvate in bud, deciduous, Crown of 5 hooded bodies seated on the tube of 



