ASCLEPIADACEAE (mILKWEED FAMILY) 667 



•^ Crowji upon a column shorter than the globular mass of anthers and stigmas ^ 



leaves mainly alternate-scattered. 



1. A. auriculata Engelm. Glabrous, or puberalent above, 1 ra. or less high ; 

 leaves narrowly linear or Miform, 1 or 2 dm. long; umbels numerous, lateral, 

 on peduncles about as long as the slender pubescent pedicels ; column vei'y 

 short and inconspicuous; hoods emarginate, appendaged below with a pair oj 

 broad auricles. — Dry ground, Neb. and Kan., westw. and southw. June-Aug. 



2. A. floridana (Lam.) Hitchc. Minutely roughish-hairy or smoothish ; 

 leaves linear to lanceolate ; umbels few, terminal or lateral, on peduncles of 

 about the length of the slender pedicels; column about 1 mm. long; hoods 

 entire^ not auricled. (^A. longifolia Ell.) — Prairies and pine barrens, O. to Ont., 

 Minn., Tex., and Fla. June-Sept. 



** Crown sessile, the oblong hoods nearly equaling the anthers; leaves often 



opposite and broader. 



3. A. viridifl5ra Ell. ^Minutely soft-downy, becoming smoothish ; stems 

 ascending, 8-8 dm. high ; leaves oval to oblong, thick, 4-10 cm. long ; umbels 

 nearly sessile, lateral, dense and globose ; flower (when the corolla is reflexed) 

 1 cm. long, short-pediceled. — Dry soil, jiass. to Sask., and southw. June-8ept. 

 Var. LAxcEOLAT.v (Ives) Gray. Leaves lanceolate, 6-10 cm. long. (Var. Ivesii 

 Britton.) — Range of the typical form. Var. lixe.Vris Gray. Leaves elon- 

 gated, linear ; stems low ; umbels often solitary. — Man., N. Dak., and southw. 



4. A. lanuginbsa (Nutt. ) Dene. Hairy, low (1-2.5 dm. high) ; leaves lan- 

 ceolate or ovate-lanceolate; umbel solitary and terminal, peduncled; flowers 

 smaller ; pedicels slender. — Prairies, 111. to Minn., and westw. July. 



4. GON6lOBUS Michx. Angle-pod 



Crown of free leaflets, which are truncate or obscurely lobed at the apex, 

 where they bear a pair of flexuous awns united at base. Anthers nearly as in 

 Asclepias ; pollen-masses oblong, obtuse at both ends, fixed below the summit 

 of the stigma to the descending glands. Follicles elongate-ovoid to lanceolate, 

 smooth. Seeds with a tuft, as in Asclepias. — A perennial twining herb, smooth, 

 with opposite heart-ovate and pointed long-petioled leaves, and small whitish 

 flowers in raceme-like clusters on slender axillary -peduncles. (Name from yuvia, 

 an angle, and \o^6s, apod, from the angled fruit.) Exslexia Nutt. 



1. G. laevis Michx. Climbing, 3— 4 m. high ; leaves 3.5-12 cm. wide. {Ens- 

 lenia albida Nutt.; Ampelanus aJbidus Britton.) — River-banks and thickets, 

 Pa. to 111., Kan., and southw. July-Sept. 



5. CYNANCHUM L. 



Crown flat, simple. Anthers, smooth follicles, and seeds much as in Asclepias. 

 — Herbs, often twining. (An ancient name for some plant supposed to be 

 poisonous to dogs, from kvwv, dog, and &yx€(-f, to strangle.) Vixcetoxicum 

 Medic, Moench, etc., not Walt. 



1. C. xiGRUM (L.) Pers. Twining, nearly smooth; leaves ovate or lance- 

 ovate ; flowers small, dark purple, in an axillary cluster, on a peduncle shorter 

 than the leaves ; corolla pubescent within. — Waste places and old fields, e. 

 Mass. and Vt. to Pa, and O. June-Sept. (Introd. from Eu.) 



2 C. Vixcetoxicum (L.) Pers. Suberect, 3-<) dm. high ; leaves ovate- 

 lanceolate ; flowers greenish-white ; corolla glabroufi. — Escaped from cultivation 

 in s. Ont., near Niagara Falls (according to J. M. Macoun). (Introd. from Eu.) 



6. VINCETOXICUM Walt. Angle-pod 



Corolla wheel-shaped, sometimes reflexed-spreading ; the lobes convolute in 

 the bud. Crown small, aimular or cup-shaped, in the throat of the corolla. 

 Anthers partly hidden under the flattened stigma, opening transversely. Pollen- 



