Dioscorea 



DlOSCOREACEAE 



331 



o 5o 



Map 678 



Dioscorea villosa L. 



50 



Map 680 

 Dioscorea quaternata (Walt.) Gmel. 



1. Dioscorea hirticaulis Bartlett. Map 677. This species is found in low 

 woodland that usually is inundated at some time of the year, associated 

 with pin oak, sweet gum, red maple, and black gum. Like all the other 

 Indiana species it has both glabrous and pubescent forms and I have 

 not seen intermediates. I think that they are distinct but a paucity 

 of specimens does not warrant a decision in the matter. 



Va., N. C. to Ga. and Ind. 



2. Dioscorea villosa L. Wild Yam-root. Map 678. Rather frequent in 

 the northern half of the state, becoming rare or infrequent in the southern 

 part. It prefers moist soil of rich woodland. The lower surface of the 

 blades of all the specimens I have seen is densely pubescent. The glabrous 

 variety has not been found in the state. This species and the preceding 

 can be determined definitely only when the whole plant, including the 

 rhizome is at hand. The long, slender rhizomes with few or no laterals 

 are conclusive in naming this species. 



Mass. to Minn., southw. to Va. and Tex. 



3. Dioscorea glauca Muhl. (Dioscorea quaternata var. glauca (Muhl.) 

 Fern. Rhodora 39: 399-400. 1937.) Map 679. This species prefers 

 slopes of deep ravines and is usually associated with beech and sugar 

 maple. When the leaves are not glaucous beneath this species is difficult to 

 separate from the next species. Small, in his Flora of the Southeastern 

 States, separates them on the size of the staminate flowers. In the typical 

 form the lower surface of the leaves is sparsely pubescent on the principal 

 nerves ; the number of leaves in the basal whorl is usually 6, their margins 

 rarely undulate ; rhizomes much branched. The wings of the seed of all of 

 my plants are white while those of the next species are brown. 



Pa. to Mo., southw. to S. C. and Ark. 



4. Dioscorea quaternata (Walt.) Gmel. Map 680. Infrequent in the 

 state within the area shown on the map. It is found in wooded ravines, on 

 the crests of chestnut oak ridges, and on the bluffs of the Ohio River. 



