330 Dioscoreaceae Dioscorea 



43. DIOSCOREACEAE Lindl. Yam Family 

 1252. DIOSCOREA [Plumier] L. 



[Bartlett. The source of the drug Dioscorea, with a consideration of the 

 Dioscorese found in the United States. U.S. Bureau of Plant Industry, 

 Bull. 189: 1-29. 1910.] 



The rhizomes of the species that occur in Indiana are used in medicine. 

 Their great variation in size and shape led Bartlett to make a study of the 

 species of the United States. There are authors who have not accepted 

 Bartlett's division of the genus and it offers an interesting study to one 

 with accumulated data who can restudy the genus with all the species 

 under cultivation. All of the species are perfectly hardy at Bluffton. About 

 10 years ago I began to plant rhizomes from all parts of the state and I 

 now have a considerable number of plants but failure to use permanent 

 labels prevents me from drawing conclusions. The following key and treat- 

 ment of our species should be regarded as only provisional until our species 

 are better understood. 



Lower leaves alternate, approximate, or in whorls of 3 (or 4); rhizomes linear, the 

 older ones with lateral branches, dried ones generally 5-8 (10) mm in diameter. 

 Internodes, at least the lowermost, more or less spreading-pubescent with stiff, color- 

 less or reddish brown hairs mostly 0.2-0.5 mm long; lower surface of the leaves 

 pubescent or glabrous; staminate inflorescence axillary, in short and narrow 

 panicles up to 6 cm long; pistillate inflorescence in axillary racemes, developing 

 up to 10 triangular capsules; capsules usually slightly obovoid or elliptic and 

 broader than long, up to 24 mm long; seed broadly winged, up to 16 mm long, 



the body of the seed mostly about 5 mm wide 1. D. hirticaulis. 



Internodes glabrous; staminate inflorescence axillary, in widely spreading panicles up 

 to 12 cm long; pistillate inflorescence, capsules, and seed similar to the pre- 

 ceding but the racemes usually developing 5 or 6 capsules 2. D. villosa. 



Lower leaves in whorls of 4-9, mostly of 5-7, ovate-cordate; rhizomes more or less 



contorted or, if linear, with many short, knoblike branches, usually (8) 10-15 mm 



in diameter. 



Leaves glaucous beneath, usually until maturity; leaves of lowest whorl 5-9, generally 



6, the margins rarely somewhat undulate, sparsely pubescent on the principal 



veins beneath, rarely a plant with dense pubescence; petioles at the insertion of 



the blade usually more densely pubescent than the blade, glabrous nearly to the 



base; nodes of stem usually minutely puberulent at the base of the petioles; 



capsules up to 6 in a raceme, up to 30 mm long, variable in shape; sometimes 



broadly elliptic and obovoid ones found on the same raceme; seed up to 20 



mm long, the margins colorless, body orbicular, up to 5 mm in diameter; rhizomes 



generally about 10 mm in diameter, contorted, extremely variable in shape, the 



many laterals diverging in all directions 3. D. glauca. 



Leaves green beneath, those of the lowest whorl generally 4-6; margins of the first 

 whorl of leaves and often the second and third whorl conspicuously undulate; 

 lower surface of blades glabrous (although there are specimens with the lower 

 surface densely pubescent that are referred to this species complex); petioles of 

 typical specimens glabrous at insertion of the blade as well as at the base; 

 internodes generally glabrous (except the pubescent forms); capsules like the 

 preceding but usually much larger; seed similar but larger and with a brown 

 wing; body orbicular and about 5 mm in diameter; rhizomes mostly about 15 

 mm in diameter, generally of a linear type but with numerous knoblike laterals. 

 4. D. quaternata. 



