ASCLEPIADACEAE (MILKWEED FAMILY) 667 



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

 leaves mainly alternate- scattered. 



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

 leaves narrowly linear or filiform, 1 or 2 din. 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. 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. 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. LANCEOLA.TA. (Ives) Gray. Leaves lanceolate, 6-10 cm. long. (Var. Ivesii 

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

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



4. A. laauginbsa (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 yuvla, 

 an angle, and Xo/36s, 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., 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 utiw, dog, and &^x iV -> t strangle.} VINCETOXICUM 

 Medic., Moench, etc., not Walt. 



1. C. N!GRUM (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. VINCETOXICUM (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- 



