182 APOCYNA.CEAE 



Leaves ovate or those of the branches lanceolate. 2. A. brevifoHa. 



Leaves narrowly lanceolate, those of the branches linear. 3. A. Easlwoodiana. 

 Plant densely villous. 4. A. tomentosa. 



2. APOCYNUM (Tourn.) L. Dogbane, Indian Hemp. 



Corolla fiilly twice as long as the calyx; its lobes spreading in anthesis. 

 Leaves more or less pubescent beneath. - 



Sepals broadly lanceolate; corolla open campanulate; leaves thick, dark green, 

 decidedly pubescent benea,th. 

 Leaves oval, acute at both ends; plant usually tall. 1. A. androsemaefolium. 

 Leaves more or less ovate, rounded, truncate, or cordate at the base; plant low, 

 diffuse. 

 Leaves rounded, rarely truncate at the base; stem and branches glabrous. 



2. A. scopulorum. 

 Leaves subcordate or at least truncate at the base; stem and branches 

 mostly pubescent. 3. A. pumilum. 



Sepals narrowly lanceolate: corolla narrower, almost cylindro-campanulate: leaves 

 pale green, pubescent merely on the petioles and the veins beneath, the lower 

 truncate, the upper acute at the base. 4. A. lividum. 



Leaves perfectly glabrous. 



Leaf-blades lanceolate or rarely ovate, pale; corolla almost white, narrowly cam- 

 panulate. 5. A. convallarium. 

 Leaves broadly or roimded ovate, thicker and dark green; corolla rose-colored, 

 open campanulate. 

 Sepals acute; corolla 5-6 mm. long. 6. A. ambigens. 

 Sepals acuminate; corolla 7-9 mm. long. 7. A. macranthum. 

 Corolla less than twice as long as the calyx ; its lobes erect or nearly so. 



Leaves acute at the base, petioled. 8. A. cannabinum. 



Leaves, at least those of the main stem, tinincate or subcordate at the base and sub- 

 sessile. 9. A. sibiricum. 



Family 106. ASCLEPIADACEAE. Milkweed Family. 



Crowns wanting; corolla urceolate or campanulate; stem twining. 1. Astephanus. 

 Crowns present; corolla rotate or open-campamjlate. 



Crowns double, the outer of a shallow undulate ring ; plants twining. 



2. PHILtBERTBLLA. 



Crowns simple; plants erect or decumbent, not twining. 

 Corolla-lobes reflexed during anthesis. 



Hoods of the crown crestless or with an obscure crest within. 



3. ACERATES. 



Hoods of the crown with a horn-like or tooth-like crest within. 



4. ASCLEPIAS. 

 Corolla-lobes erect-spreading during anthesis. 5. Asclepiodora. 



1. ASTEPHANUS R. Br. I. A. utahensis. 



2. PHILIBERTELLA Vail 



Crowns separate by a short column ; stem glabrous. 1 . P. cynanchoides. 



Crowns contiguous; stem puberulent or pubescent. 2. P. heterophylla 



3. ACERATES Ell. Green Milkweed. 



Auricles of the hoods when present, coneea.led within; leaves oval to linear. 



Umbel solitary, terminal; plant hirsute. 1. A. lanuginosa. 



Umbels several, lateral; plant glabrate or tomentose when young. 2. A. mridiflora. 

 Auricles of the hoods conspicuously spreading; umbels lateral; leaves narrowly linear. 

 Hoods emargiuate or truncate at the summit, crestless within; umbels distinctly 



peduncled. 3. A. auriculata. 



Hoods trilobed at the summit, with ah internal crest-like midrib terminating in the 

 middle lobe; umbels subsessile or on very short peduncles. 4. A. angustifolia. 



4. ASCLEPIAS (Tourn.) L. Milkweed, Silkweed, Butterfly-weed. 

 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) . 



Folhcles 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. 

 Folhcles 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. 



