372 ASCLEPIADACEAE 



Family 124. ASCLEPIADACEAE. 



Milkweed Family. 



Perennial herbs, vines or shrubs, usually with milky juice. Leaves opposite, 

 alternate or verticillate, without stipules. Flowers mostly umbellate, perfect and 

 regular, commonly 5-merous. Calyx free from the ovary, 5-parted or 5-lobed, the 

 segments usually imbricated. Corolla 5-lobed to 5-cleft, varying from funnelform 

 to rotate, the lobes commonly valvate in the bud. Crown present, situated just out- 

 side the stamens and adnate to them or to the corolla, 5-lobed or 5-parted. Stamens 

 5, inserted on the corolla-tube, usually near the base, distinct or commonly mona- 

 delphous ; anthers basifixed, connivent around the stigma, introrsely 2-celled, the 

 sacs appendaged or tipped with a scarious, erect or inflexed appendage, sometimes 

 appendaged at base ; pollen coherent into glandular or granular masses, one or 

 rarely two of these masses in each pollen-sac. and connected with the stigmas in 

 pairs or rarely in fours by 5 glandular corpuscles alternate with the anthers. Ovary 

 bicarpellate ; styles 2, connected at the apex by the peltate discoid stigma ; ovules 

 numerous, pendulous, mostly anatropous. Fruit a pair of several- to many-seeded 

 follicles. Seeds compressed, usually appendaged by a conspicuous coma ; endosperm 

 cartilaginous, usually scanty : embryo generally large ; cotyledons flat. 



About 250 genera and over 2,000 species, of wide geographical distribution, most abundant in tropical 

 and warm temperate regions. 



Stems twining. 



Crown wanting; corolla-lobes cucullate; flowers in umbels. 1. Astephanus. 



Crown present; corolla-lobes plane. 



Flowers in umbels; crown double, the outer a mere ring, the inner of 5 fleshy hood-like scales; pollen- 

 masses pendulous to the caudicle. 2. Funastrum. 



Flowers solitary in the axils; crown single, of S thin white scales; pollen-masses horizontal to the 

 caudicle. 3. Conolobus. 



Stems not climbing. 



Corolla-lobes reflexed in anthesis; hoods distinct from each other. 



Stems flattened, prostrate; anther-wings lunate; hoods slit down the back into 2 valves; horns none. 



4. Solanoa. 

 Stems terete, erect or decumbent; anther-wings broadened at the base and angled on the back; hoods 

 variously slit; horns present (except A. cordifolia and calif arnica). 5. Asclepias. 



Corolla-lobes erect-spreading in anthesis; hoods united to each other by a lobed disk. 6. Asclepiodora. 



1. ASTEPHANUS R. Br. Mem. Wern. Soc. 1 : 54. 1809. 



Shrubs or suffrutescent plants, the stems often slender and twining-. Leaves opposite, 

 slender or reduced to spines. Flowers small, in few-flowered cymes or umbellate, sessile 

 in the axils or pedunculate. Calyx 5-parted, the segments acute. Corolla urceolate or 

 nearly campanulate, 5-lobed. Crown wanting. Stamens inserted on the base of the corolla- 

 tube; anthers with a short inflexed appendage at apex; pollen-masses solitary in each 

 pollen-sac, pendulous. Stigma obtusely conic or rostrate at apex. Follicles terete, acumi- 

 nate, smooth. [Name Greek, meaning without crown.] 



A genus of about 25 species, inhabiting southern Africa, Madagascar, South America, Cuba, Mexico, 

 and the following species in southwestern United States. Type species, Astephanus triflorum (L. f.) R. Br. 



L Astephanus utahensis Engelm. Utah Astephanus or Deboltia. Fig. 3832. 



Astephanus utahensis Engelm. Amer. Nat. 9: 349. 1875. 



Astephanus filifolium Engelm. ex Benth. & Hook. Gen. PI. 2: 747. 1876. 



Cynanchum utahense Woodson, Ann. Mo. Bot. Card. 28: 215. 1941. 



Stems numerous arising from the subterranean woody branches of the taproot, very slender, 

 spreading or twining, 25-50 cm. long, herbage pale gray-green, glabrous or sparsely puberulent. 

 Leaves narrowly linear, 1-3 cm. long, 0.5-1.5 mm. wide, spreading or reflexed; umbels pe- 

 duncled, few- to many-flowered, subtended by a few subulate bracts ; rays 4-8 mm. long ; 

 calyx-lobes narrowly lanceolate, 1.5 mm. long, strigose; corolla yellowish, short-campanulate, 

 2-2.5 mm. long, the lobes cucullate with the apex strongly curved inward, papillose-puberulent 

 within ; anthers unappendaged at apex ; folHcles long-acuminate, seeds rough-granulate. 



Sandy soils, Lower Sonoran Zone; Mojave and Colorado Deserts, California, to Nevada, southern Utah, 

 and Arizona. Type locality: drifting sand hills near St. George, Utah. April-July. 



2. FUNASTRUM Fourn. Ann. Sci. Nat. VL 14:388. 1882. 



Perennial herbs or shrubby plants, with usually twining stems, herbage glabrous, 

 pubescent or tomentose. Leaves opposite, petioled, variously shaped. Flowers in axillary 

 pedunculate umbels. Calyx 5-parted, the lobes narrow, acute. Corolla deeply 5-parted, 

 the segments often spreading or reflexed in age. Outer crown a low ring, the inner a 



