Fam. 110. Asclepiadaceae R. Br. Milkweed Family 



Perennial herbs, vines or shrubs with milky juice; leaves opposite, whorled 

 or sometimes alternate, without stipules; flowers perfect, regular, usually umbellate, 

 commonly 5-merous; calyx deeply lobed, the lobes mostly imbricate; corolla 

 5-lobed or -cleft, the lobes commonly valvate in bud; a 5-lobed crown is usually 

 present between the corolla and stamens and is adnate to either or both; stamens 5, 

 inserted on the corolla tube usually near its base, the filaments monadelphous or 

 sometimes distinct; anthers united and tipped with a scarious membrane inflexed 

 on the summit of the stylar disk; pollen grains united into waxlike or granular 

 pollinia; carpels 2. with distinct superior ovaries and styles but united above by the 

 peltate discoid stigma; fruit of 2 follicles (or 1 by abortion); seeds many, com- 

 pressed, usually with long coma. 



About 130 genera and 2.000 species widely distributed but most frequent in 

 warm regions. 

 1. Stamen column or its base with 1 row of flat thin appendages. ...2. Cynanchum 



1. Stamen column or its base surrounded by 5 separate fleshy-inflated or fleshy- 



thickened erect or spreading appendages (hoods) (2) 



2(1). Stems prostrate to erect, not twining; base of corolla without a fleshy 

 disk under the separate appendages 1. Asclepias 



2. Stems twining, at least toward tips; corolla with a fleshy disk at base under 



the appendages 3. Sarcostemma 



1. Asclepias L. Milkweed. Silkweed 



Herbs, rarely fruticose or suffruticose. perennial or rarely annual, usually 

 laticiferous; leaves usually decussate, infrequently whorled or irregularly approxi- 

 mate; inflorescence terminal or interpetiolar, umbelliformly cymose, very rarely 

 reduced to a solitary flower; calyx lobes 5, equal, divided nearly to the receptacle, 

 bearing few to many minute glandular squamellae within at the base; corolla 

 rotate, the lobes 5, valvate, equal, reflexed. spreading or rarely erect; gynostegium 

 definitely stipitate to sessile; corona of 5 hoods attached to the column and 

 subtending the conniverit anthers; hoods cucullate to clavate with various modifi- 

 cations, more or less stipitate to sessile and deeply saccate at the basal attachment 

 to the column, usually bearing an internal horn or crest; anthers 2-celled, with 

 more or less prominent corneous marginal wings enclosing the 5 stigmatic 

 chambers and with membranaceous apical appendages; pollinia paired and pen- 

 dulous from the translator arms, flat and uniformly fertile, enclosing granular 

 pollen with thin hyaline intine; anther head peltate, more or less pentagonal; fruit 

 follicular, containing many compressed comose or rarely naked seeds. 



About 1 20 species that are native mostiy to the Americas. 



1. The complete hoods or only their apical portion widespread from the anther 

 head 1. A. speciosa. 



1. The hoods erect to suberect, more or less parallel to and contiguous with 



the anther head (2) 



2(1). Leaves typically broad, suborbicular to ovate-elliptic or elliptic to oblong- 

 lanceolate (3) 



2. Leaves typically narrow, lanceolate to narrowly triangular-lanceolate or linear- 



lanceolate to filiform, sometimes ovate (5) 



3(2). Hoods shorter than to only slightly longer than the anther head; corolla 

 white 10. A. texana. 



3. In natural position the hoods extending at least a third longer than the anther 



head (4) 



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