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ASCLEPIADACEAE. 
Family no. ASCLEPIADACEAE Lindl. Milkweed Family. 
Corolla-lobes reflexed during anthesis. 
Hoods of the crown crestless within or with an obscure crest-like midrib. 
i. Acerates. 
Hoods of the crown each with a horn-like process within. 2. Asclepias. 
Corolla-lobes erect-spreading during anthesis ; hoods with a crest at least above. 
3. Asclepiodora. 
1. ACERATES Ell. Green Milkweed. 
Auricles of the hood, when present, concealed within; leaves oval to linear- 
lanceolate. 1. A. virididora. 
Auricles of the hoods conspicuously spreading; umbels lateral; leaves narrowly 
linear. 
Hoods emarginate or truncate at the summit, crestless within; umbels dis¬ 
tinctly peduncled. 2. A. auriculata. 
Hoods trilobed at the summit with an internal crest-like midrib terminating in 
the middle lobe; umbels subsessile or on very short peduncles. 
3. A. angustifolia. 
1. Acerates viridiflora (Raf.) Eat. In dry or sandy soil from Mass, and 
Mont, to Fla. and N. M.—Alt. 4000-6000 ft.—Fossil Creek, Larimer Co.; 
Horsetooth Mountain; Boulder; Berkeley; Valverde. 
2. Acerates auriculata Engelm. On dry plains from Neb. and Colo, to 
Tex. and N. M.—Alt. 4000-5000 ft.—Canon City; Ft. Collins; Horsetooth 
Gulch; Denver; Valverde; Montclair. 
3. Acerates angustifolia (Nutt.) Decaisne. ( Asclepias stenophylla A. 
Gray) In sandy soil from S. D. and Colo, to Mo., Tex. and N. M.—Exact 
locality not given. 
2. ASCLEPIAS L. Milkweed, Silkweed. 
Leaves orbicular to linear-lanceolate, opposite. 
Follicles with soft spinulose processes, tomentose; leaves large and broad, 
tomentose, transversely veined, oval or ovate. 1. A. speciosa. 
Follicles without processes. 
Flowers very large ; petals over 1 cm. long ; column none ; horns included in 
the hoods; leaves almost orbicular, subcordate at the base. 
2. A. cry p toe eras. 
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. 
3. A. latifolia. 
Plant tomentulose ; column half as long as the anthers. 
4. A. arenaria. 
Leaves ovate or lanceolate, or rarely oval, acute. 
Leaves ovate or ovate-lanceolate, more or less tomentose at least when 
young; hoods ovate-oblong to lanceolate, much exceeding the stamens. 
5. A. Hallii. 
Leaves linear-lanceolate; hoods truncate, little if any longer than the 
anthers. 
Column short; leaves pale, tomentose or puberulent when young. 
Hoods about half as long as the anthers; umbels peduncled. 
6 . A. brachystephana 
Hoods only slightly shorter than the anthers ; umbels subsessile. 
7. A. uncinalis. 
Column more than half as long as the anthers ; corolla purple; leaves 
glabrous. 8. A. incarnata. 
