MILKWEED FAMILY 671 



1. A. lanuginosa (Nutt.) DC. Stem erect, 1-4 dm. high; leaves oblong or 

 elliptic, short-petiolcd, 3-10 cm. long; corolla greenish; lobes oblong, about 5 

 mm. long; hood purplish, oblong, with an auricle or fold on the ventral margms. 

 Prairies: 111.— Minn.— Mont.— Wyo. Je-Au. 



2. A. viridiflora (Raf.) Eat. Stem 2-6 dm. high, often decumbent; leaves 

 oval or oblong and obtuse or retuse or acute, or elongated lanceolate and acumin- 

 ate (var. Ivesii Britton), or narrowly linear (var. linearis A. Gray), becommg 

 leathery, with undulate margins; umbels sessile or nearly so, many-flowered; 

 corolla-lobes oblong-lanceolate, about 5 mm. long; hood dull purple or at least 

 tinged wnth purple, lance-oblong, entire except for the small infolded auricles at 

 the base. Dry or sandy soil: Mass.— Fla.—N.M.— Mont. riaifiSubmonL 



Je-Jl. 



3. A. " auriculata Engelm. Stem 2-8 dm. high, mostly solitary; leaves 

 alternate, scattered, narrowly hnear,5-15 cm. long, with scabrous, often revohite 

 margins; corolla-lobes greenish, about 4 mm. long; hood yellowish, with purplish 

 keel erect emarginate or truncate, the involute sides with broad auricles at the 

 base. Plains and prairies: Neb.— Utah— X.M.— Tex. Plain— Sub moiiL Je- 



Au. 



4. A. angustifolia (Nutt.) Dec. Stem several from a thick rootstock, 3-6 

 dm high, puberulent or glabrate in age; leaves narrowly linear, 5-12 cm. long, 

 revolute-margined ; umbels subsessile; corolla-lobes 5 mm. long, oblong, greenish; 

 hood white, erect, as high as the anthers, laterally compressed, 3-dentate at the 

 apex the inner margins with an erose truncate lobe. Asclepias stenophylUi A. 

 Gray. Dry plains: S.D.— Colo.— Tex.— Mo. Plain. Je-Au. 



TTE 



4. ASCLEPIAS (Tourn.) L. Milkweed, Silkw^eed, B 



Perennial herbs, with deep taproots, sometimes woody at the base. Leaves 

 opposite, alternate, or whorled. Flowers perfect, regular, m axillary or terminal 

 umbels. Calyx small, usually with small glands at the base of the 5 lobes. 

 Corolla rotate, deeply 5-cleft; lobes valvate-convolute m bud, reflexed in anthesis. 

 Hoods of the croxra involute, arising from the base of the corolla-lobes or on a 

 short column, concave, hooded, bearing within a horn- or tooth-like projection, 

 and sometimes additional processes between the anthers Follicles fusiform, 

 naked or with soft processes or warty. Seeds mostly with a coma. 



Plant more or less hirsute; hoods orange: leaves mostly alternate; ^"ui^e not^nulk>^ 



Plant not liirsute; hoods greenish, purplish, yeUowish. or white; leaves' mostly opposite 



or verticillate; juice milky. ^^„*. -vr^ ia\ 



Leaves orbicular to linear-lanceolate, opposite (except No. 14). ^.^^^^r, 



FoUicli with soft spinulose processes, tomentose; leaves large and broad, tomen- 



tose. transversely veined, oval or ovate. 

 Hoods oblong-ovate, obtuse, slightly exceeding the stamens. ^^^.^^^ 



Hoods lanceolate, produced, about three times as long ^^^^^^l^"^^'^ 



^"^ M^we^'ver^^^ Farg'eTpltals over 1 cm. long; column none; coroUa spherical in 

 -*^^^Y.?rf:J..t^'^s included in the hoods; leaves ahnost orbicular, sub-cordate 



4. A. crypioceras. 



=iV^ri r.T ^TTinll • T>etals much less than 1 cm. long; column usuaUy 



at the base. 



oresent and horns exserted. , ,.. , i,* 



Leav^ broadly oval or rectangular-oval or nearly orbicular, obtuse op 



retuse at both ends; umbels sessile. ^ 

 Plant pubenilent when young, glabrate m age; column very short. 



Plant tomentulose; column half as long as the anthers. 



6. A. armaria. 



Leaves ovate or lanceolate, or rarely oval, acute. * , ♦ t. 



L^ves ovate or ovate-lanceolate, more or less tomentose, at least when 



Hoods^tmncate. sUghtly longer than the anthers; leaves sessile, 



with rounded or subcordate bases. 7. A. erosa. 



Hoods ovate-oblong to lanceolate, much exceedmg the stamens; 



leaves petioled. , t. - * 



CoroUa yellowish; hoods with a tooth on each margin, not 

 atiricled or gibbous at the base ; peduncles shorter than the 

 pedicels. 8- ^- ovalifoha, , 



