ASCLEPIADACEAE (MILKWEED FAMILY) 667 



* Crown upon a column shorter than the globular mans of anthers and stigmas; 



leaves mainly alternate- scattered. 



1. A. auriculata Engelui. Glabrous, or puberulent above, 1 ra. or less high ; 

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

 on peduncles about as long as the slender pubescent pedicels ; column very 

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

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



2. A. iloridana (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. viridiflbra Ell. Minutely soft-downy, becoming smoothish; stems 

 ascending, 3-8 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, Mass, to Sask., and southw. June-Sept. 

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

 Britton. ) Range of the typical form. Var. LINE\RIS Gray. Leaves elon- 

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



4. A. lauuginbsa (Nutt.) Dene. Hairy, low (1-2.6 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 ywvla, 

 an angle, and \o6s, a pod, from the angled fruit.) ENSLENIA Nutt. 



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

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

 Pa. to 111. , t 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 K&WV, dog, and Hyx fl - v i to strangle.) VINCETOXICUM 

 Medic., Moench, etc., not Walt. 



1. C. NIGRUM (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. ViNCET6xicuM (L. ) Pers. Suberect, 3-6 dm. high; leaves ovate- 

 lanceolate ; flowers greenish-white ; corolla glabrous. 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, annular or cup-shaped, in the throat of the corolla. 

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



