270 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. 



i. ACERATES Ell. GREEN MILKWEED. 



Auricles of the hood, when present, concealed within ; leaves oval to linear- 

 lanceolate, i. A. viridiflora. 

 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 stcnophylla 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. i. A. speciosa. 



Follicles without processes. 



Flowers very large ; petals over i cm. long ; column none ; horns included in 

 the hoods ; leaves almost orbicular, subcordate at the base. 



2. A. cryptoceras. 

 Flowers middle-sized or small ; petals much less than i 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. 



