(Reprinted from the Huli.btin of tuf Tokrky Botanicai. Ci.i'ii, 28: Anpiisi, 1901.] 



Studies in the Asclepiadaceae.— V. A New Species of Vincetoxicum 



from Chihuahua 



By Anna Murray Vail 

 (With Plate 30) 



Vincetoxicum Wootonii 



{Gonolobus A. Gray, non Michaux) 



A low branching perennial herb with small axillary sub- 

 umbellate clusters of dull greenish-purple flowers : stems angled, 

 puberulent with short, apparently twisted hairs : leaves opposite, 

 on petioles 3-5 mm. long ; blades 7 mm.-i cm. long, pale gray- 

 ish-green, round-ovate, obtuse at the apex, cordate, the basal lobes 

 rounded, obtuse, thick and coriaceous, glabrous above, puberulent 

 on the veins beneath, ciliate : peduncles 5-12 or 15 mm. long, 

 3—6- or /-flowered, puberulent: pedicels very slender, 4-6 mm. 

 long, puberulent, bracteolate at base : calyx-segments ovate-lanceo- 

 late, less than 2 mm. long, acute, puberulent, purplish, eglandu- 

 lose at the base within : corolla-segments rotately spreading, dull 

 yellowish-green, thickish, less than 4 mm. long, oblong-ovate, 

 obtuse, glabrous, vertically reticulated, subglobose ? in bud: 

 corona saucer-shaped, 5-lobed, somewhat higher than the anthers, 

 fleshy ; lobes broadly rounded, thickened at the center on the inner 

 side, appendaged with 5 ligulate Asclepias-\\kQ incurved horns which 

 adhere to the lobe to near the middle : stigma flat, barely 5-angled : 

 pollinia obliquely semi-orbicular ; caudicles broadly winged, very 

 slender at the attachment to the narrowly oblong corpuscle. 



Nearly related to Vincctoxiann biflonim (Raf.) Heller and 

 remarkable for the small leaves and AscUpias-Vik^ horns. 



Mexico: State of Chihuahua, Colonia Garcia, Sierra Madre, 

 altitude about 7200 ft., collected by Elmer O. Wooton, no. 13, 

 June, 1899. 



Explanation of Plate 30 



Fig. I. Vincetoxicum Wootonii, slightly reduced. 



Fig. 2. Flower diagrammatically enlarged , X 5- 



Fig. 3. Flower enlarged, X 2^. 



Fig. 4. Corona diagrammatically enlarged. 



Fig. 5. Pollinia enlarged, X 50- 



485 



