MILKWEED FAMILY 671 



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

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

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

 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), becoming 

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

 the base. Dry or sandy soil: Mass. Fla. N.M. Mont. Plain Submont. 

 Je-Jl. 



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

 alternate, scattered, narrowly linear, 5-15 cm. long, with scabrous, often revolute 

 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 N.M. Tex. Plain Submont. 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, 

 re volute-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 stenophylla A. 

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



4. ASCLEPIAS (Tourn.) L. MILKWEED, SILKWEED, BUTTERFLY-WEED. 



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

 opposite, alternate, or whorled. Flowers perfect, regular, in 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 in bud, reflexed in anthesis. 

 Hoods of the crown 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; juice not milky. 



1. A. tuberosa. 

 Plant not hirsute; hoods greenish, purplish, yellowish, or white; leaves mostly opposite 



or verticillate; juice milky. 

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



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



tose, transversely veined, oval or ovate. 

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



2. A. syriaca. 

 Hoods lanceolate, produced, about three times as long as the stamens. 



3. A. speciosa. 

 Follicles without processes. 



Flowers very large; petals over 1 cm. long; column none; corolla spherical in 

 outline; horns included in the hoods; leaves almost orbicular, sub-cordate 

 at the base. 4. A. cryptoceras. 



Flowers middle-sized or small ; petals much less than 1 cm. long; column usually 



present and horns exserted. 

 Leaves broadly oval or rectangular-oval or nearly orbicular, obtuse or 



retuse at both ends; umbels sessile. 

 Plant puberulent when young, glabrate in age; column very short. 



5. A. latifolia. 

 Plant tomentulose; column half as long as the anthers. 



6. A. arenaria. 

 Leaves ovate or lanceolate, or rarely oval, acute. 



Leaves ovate or ovate-lanceolate, more or less tomentose, at least when 



young. 

 Hoods truncate, slightly longer than the anthers; leaves sessile, 



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



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



leaves petioled. 



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

 auricled or gibbous at the base; peduncles shorter than the 

 pedicels. 8. A. ovalifolia. 



