398 ASCLEPIADACE^E. (MILKWEED FAMILY.) 



hoods of the crown roundish-oval, about half the length of the incurved claw- 

 shaped horns; pods smooth. — Dry hills: common, especially southward. 



2. ACEEATES, Ell. Green Milkweed. 



Nearly as in Asclepias ; but the hoods of the crown destitute of a horn 

 (whence the name, from a privative and Ktpas, -aros, a horn). — Flowers green- 

 ish. Leaves varying from opposite to irregularly alternate, short-petioled or 

 sessile. Pollen-masses slender-stalked. 



§ 1. Divisions of the corolla reflexed, oblong : hoods of the crown erect and concave : 



umbels compactly many-flowered: pods not muricate, slender. 



* Crown not elevated; its hoods oblomj, nearly equalling the anthers. 



1. A. viridifl6ra, Ell. Minutely soft-downy, becoming smoothish ; stems as- 

 cending (l°-2° high) ; leaves varying from oval to linear, thick (l|'-4' long), 

 umbels nearly sessile, lateral, dense and globose ; flower (when the corolla is re- 

 flexed) nearly h' long, short-pedicelled. — Dry soil : common, especially south- 

 ward. July -Sept. 



2. A. lailUgindsa, Decaisne. Hairy, low (5' -12' high) ; leaves lanceolate 

 or ovate-lanceolate; umbel solitary and terminal, peduncled ; flowers not larger 

 than in the next; pedicels slender. (Probably Asclepias lanuginosa, Nutt.: cer- 

 tainly A. Nuttalliana, Torr. Acerates monocephala, Lapham, in Ed. 2, addend.) 

 — Prairies, Wisconsin (Lapham) and westward. July. 



* * Crown short-stalked, i.e. elevated above the base of the corolla; its hoods oval, 

 strongly concave, and decidedly shorter than the tips of the anthers. 



3. A. loilgifolia, Ell. Minutely roughish-hairy or smoothish ; stem 

 erect (1° -3° high), very leafy ; leaves mostly alternate-scattered, linear (3'-7' 

 long) ; umbels lateral, on peduncles of about the length of the slender pedicels ; 

 flowers 3" long when expanded. — Moist prairies, Ohio to Wisconsin and south- 

 ward. July -Oct. 



§2. AXAXTHERIX, Nutt. Divisions of the corolla ascending or barely spread- 

 ing : hoods of the crown widely spreading and somewhat incurved, slipper-shaped 

 and laterally compressed, the cavity divided at the apex by a crest-like partition : 

 umbels solitary and terminal or corymbed, loosely-flowered : pods oblong or ovate, 

 often somewhat muricate with soft spinous projections. 



4. A. paniculata, Decaisne. Almost glabrous; stems short (l°high); 

 leaves alternate, short-petioled, elongated-oblong, l'-2' wide ; umbels several in 

 a cluster, short-peduncled ; flowers large (1' in diameter), green, with a purplish 

 crown. — Prairies, Illinois (Vasey, Bebb), and southward. June. 



3. ENSLENIA, Nutt. Enslenia. 



Calyx 5-parted. Corolla 5-parted; the divisions erect, ovate-lanceolate. 

 Crown of 5 free membranaceous leaflets, which are truncate or obscurely lobed 

 at the apex, where they bear a pair of flexuous awns united at their base. An- 

 thers nearly as in Asclepias : pollen-masses oblong, obtuse at both ends, fixed 

 below the summit of the stigma to the descending glands. Pods oblong-lanceo- 

 late, smooth. Seeds with a tuft, as in Asclepias. — A perennial twining herb, 



