ASCLEPIADACEAE. 281 



anthers attached by their bases to the filaments, in- 

 trorsely 2-celled; anther-sacs tipped with an inflexed or 

 erect scarious membrane or unappendaged ; pollen co- 

 herent into waxy or granular masses. Ovary of 2 carpels ; 

 styles 2, short, connected at the summit by the peltate 

 discoid stigma; ovules numerous, pendulous. Fruit of 

 2 several-many-seeded follicles. Seeds compressed, usu- 

 ally appendaged by a long coma. 



Plants twining. 1. Philibertella. 



Plants erect or decumbent, not twining. 2. Asclepias. 



1. PHILIBERTELLA Vail. 



Twining herbs or somewhat shrubby, with opposite 

 leaves and umbellate flowers. Calyx small, 5-parted, the 

 lobes acute. Corolla campanulate or rotate, deeply 5- 

 parted, the lobes acute or obtuse, with a shallow entire 

 or undulate ring forming an outer crown in its throat. 

 The inner staminal crown consisting of 5 turgid fleshy 

 or hard scales or flattish appendages, attached in a circle 

 at the base of the sessile or slightly stalked column, 

 forming a hollow entire or undulate spreading surface 

 near the level of the conic stigmas. Follicles naked, 

 slender, attenuate at both ends or obtuse at base. 



1. P. hartwegii heterophylla (Engelm.) Vail. Stems slender, 

 twining, glabrous, puberulent or somewhat pubescent above; leaves 

 2.5-5 cm. long, 2-4 mm. wide, variable, some tapering into the 

 petiole, others with rounded and more with dilated or auriculate- 

 cordate or truncate base; corolla scarcely puberulent, 1 cm. broad, 

 its lobes acute; column sessile. 



Occasional on dry hillsides in interior valleys, growing over low 

 shrubs or herbs. 



2. ASCLEPIAS L. Milkweed. 



Perennial erect or decumbent herbs, with opposite ver- 

 ticillate or rarely alternate leaves, and flowers in ter- 

 minal or axillary umbels. Calyx 5-parted or 5-divided, 

 usually small, the lobes acute, often glandular within. 

 Corolla deeply 5-parted, the lobes mostly valvate, re- 

 flexed in anthesis. Corona-column generally present. 

 Corona of 5 concave, erect or spreading hoods, each 

 bearing within a slender or subulate incurved horn. 

 Filaments connate into a tube; anthers tipped with an 



