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3. Asclepias. Corolla reflexed, deeply 5-parted: crown as in no. 2, but with 
an incurved horn rising from the cavity of each hood: leaves usually opposite. 
4. Acerates. Corolla reflexed or merely spreading: crown as in no, 2, but with 
neither crest nor horn inside: leaves mainly alternate. 
+ ++ Stems twining: leaves mostly opposite. 
= Divisions of crown abruptly pointed or appendaged at apex. 
5. Enslenia. Corolla erect-campanulate: crown of 5 thin flat bodies each termi- 
nated by a 2-cleft tail or awn. 
6. Roulinia. Corolla rotate-spreading: crown of 5 simply and abruptly acumi- 
nate or ligulate-tipped divisions, 
== = Divisions of crown not tipped with any appendage or prolonged middle lobe. 
7. Metastelma. Corolla usually campanulate: crown of 5 flat or slender and dis- 
tinct scales or processes. 
8. Vincetoxicum. Corolla rotate, spreading: crown a fleshy 5 to 10-lobed ring 
or disk. 
* * Anthers with short if any scarious tip, borne on the margin of or close under the 
disk of the stigma: pollinia horizontal. 
9. Gonolobus. Corollarotate: crown a wavy-lobed fleshy ring: stems twining. 
1. PHILIBERTIA HBK. 
Herbaceous or shrubby twining plants, with petiolate leaves, usually 
dull-colored or parti-colored fragrant flowers in pedunculate umbels, 
calyx minutely 5-glandular within, rotate corolla, double crown (exterior 
a membranaceous ring adnate to base of corolla, interior of 5 scales ad- 
nate to base of stamen-tube or column), and rather thick smooth acu- 
minate pods. 
* Column evident, rather longer than the swollen scales of the inner crown on its summit. 
1. P. undulata Gray. Low twining, glabrous or puberulent, pale: leaves from 
lanceolate and gradually acuminate to linear from a hastately cordate base, 5 to 7.5 
em. long, the margins undulate-crisped: peduncle 6 to 10-flowered, longer than the 
petiole and pedicels: corolla dull purple, glabrous above, 12 mm. broad: outer crown 
saucer-shaped. (Sarcostemma undulata Torr.)—Western Texas. 
* * Column none or very short: peduncles equaling or surpassing the plane leaves. 
2. P. Torreyi Gray. Freely twining, densely pubescent with soft spreading hairs: 
leaves cordate-lanceolate and acuminate or sagittate, 2.5 cm. or more long: peduncle 
10 to 15-flowered: corolla white (?), 16 to 18 mm. broad; the lobes strongly villose- 
ciliate: outer and inner crowns contiguous. (Sarcostemma elegans Torr., not De- 
caisne.)—Rocky hills, southwestern Texas. 
3. P. viridiflora Britton & Rusby. Tall climbing, glabrous or glabrate: leaves 
from deeply cordate to sagittate or almost hastate, abruptly cuspidate or short-acu- 
minate, 2.5 to 6.5 em. long: peduncle 15 to 25-flowered: pedicels much longer than 
flowers: corolla white or whitish, scarcely 12mm. broad; the lobes somewhat ciliate: 
crowns separated by a very short column. (P. cynanchoides Gray.)—Along rivers, 
throughout southern Texas and adjacent Mexico. 
4, P. linearis Gray. Slender, low-twining (or erect when young), puberulent or 
glabrate: leaves narrowly linear, acute or nearly so at both ends, 2.5 cm. long: 
peduncle 8 to 10-flowered: corolla yellowish, purplish, or whitish, 8 mm. broad: 
crowns contiguous.—A species of southern Arizona, reported from western Texas 
(Havard). 
2. ASCLEPIODORA Gray. 
Nearly as in Asclepias, but with the greenish corolla-lobes ascending 
or spreading, the hoods destitute of a horn (widely spreading and some- 
