ASCLEPIADACEAE (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 suhsessile ; central cyme 

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

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

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

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



Var. pub^scens (K. Br.) DC. Calyx and pedicels pubescent ; leaves white- 

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



Var. nemorale (G. S. Miller) Fernald. Leaves mostly spreading or drooping 

 on elongate (1-1.5 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, hypericifolium 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 

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

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

 explained under the typical genus Asclepias. 



Tribe I. CYNANCHEAE. Anthers tipped with an iuflexed or sometimes erect scarious mem 

 brane, the cells lower than the top of the stigma ; pollinia 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 iu no. 1, but with an incurved horii 



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

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

 nor horn Inside. Leaves mainly altei-nate. 



* * Stems twining ; leaves mostly opposite. ' 



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



tail or awn. 



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



Tribe II. VIWCETOXfCEAE. Anthers with short if any scarious tip, borne on the margin of 

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



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



1. ASCLEPI0D6rA 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. Folli- 

 cles ovoid, often somewhat muricate with soft spinous projections. ('A(r/cX777rt6s, 

 and bCjpov or dcoped, the gift of Aesculapius.) 



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

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

 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. ASCLEPIAS [Tourn.] L. Milkweed. Silkwebd 



Calyx persistent ; divisions small, reflexed. Corolla deeply 5-parted ; divisions 

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



