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



from Chihuahua 



By Anna Murray Vail 



(With Plate 30) 



Vincetoxicum Wootonii 



{Gojwlobus 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 7 -flowered, puberulent: pedicels very slender, 4-6 mm. 

 * on g> 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 AsclepiasAikt 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 Vincetoxicum bifiorum (Raf.) Heller and 

 remarkable for the small leaves and Asc/epias -like 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 jo 



*IG. 1. Vincetoxicum Wootonii, slightly reduced. 



*ig. 2. Flower diagrammatically enlarged, X 5- • 



FlG - 3- Flower enlarged, X 2>£. 



* IG - 4- Corona diagrammatically enlarged. 



Fig. 5. Pollinia enlarged, X 5°- 



485 



