Vail: Studies in the Asclepiauaceae 431 



crown 5 -parted, to below the middle ; segments thick and fleshy, 

 broadly rounded at the apex, each with an internal ligulate horn 

 or process arising from near the base, exceeding the anthers and 

 incurved over them: stigma 5 -angled : pollinia quadrate on 

 slender, winged caudicles, corpuscle narrowly oblong. Follicles 

 not seen. 



" Slender vine-like plant, flower purplish," Cadena, Mexico, 



Dr. Gregg, May 8, 1847. 



The specimen described here is in the Herbarium of Columbia 

 University and was included by Dr. Torrey in his description of 

 Gonolobus prodiictns and was ticketed under that name by Dr. 

 Gray when he revised the Torrey Collection for the Synoptical 

 Flora. It is closely allied to Vincetoxicum acuminatum {Gonolo- 

 bus aanninatns A. Gray, Proc. Am. Acad. 21 : 399. 1 888-6) as well 

 as to V. productum {Gonolobus prodiictus Torr.) All three species 

 belong in Dr. Gray's section Chthamalia and without careful dis- 

 section could scarcely be distinguished one from the other, except 

 that V. Grcggii has a more rotately spreading corolla than its con- 

 geners. 



There are marked differences in the pollinia of the three species. 

 In V. prodiictnm the pollinia are spreading and perhaps subpendu- 

 lous, obliquely oblong, twisted (?) and somewhat bent or dented 

 at the middle ; the caudicles are apparently winged and the cor- 

 puscle is oblong, also appearing as if winged. The pollinia of V. 

 acuminatiim are more truly horizontal, subovoid, rounded on one 

 side and straight on the other, on broad caudicles, with a broad 

 corpuscle. V. Grcggii has ovoid-quadrate pollinia, with very 

 slender, somewhat twisted caudicles and a slender oblong cor- 

 puscle. In this last species the leaves are smaller than in the two 

 others, the corolla is more rotately spreading, the crown is more 

 deeply parted and the internal ligules are free and incurved over 

 the anthers. The pollinia and crown characters of V. Grcggii are 

 also nearly those of Gonolobns bifidiis Hemsley, but in that species 

 the corolla is much smaller and truly rotate. In V. acinnina- 

 tiim the crown -segments are quadrate at the apex and the internal 

 processes are short, barely free at the apex. 



