LETTER OE TRANSMITTAL 



U. S. Department of Agriculture, 



Bureau of Plant Industry, 



Office of the Chief, 

 Washington^ D. 6'., July 20, 1910. 



Sir : I have the honor to transmit herewith, and to recommend for 

 publication as Bulletin No. 189 of the series of this Bureau, a manu- 

 script entitled " The Source of the Drug Dioscorea, with a Considera- 

 tion of the Dioscorere found in the United States," prepared b}^ Mr. 

 Harle}" Harris Bartlett, Chemical Biologist in the Office of Drug- 

 Plant Investigations, and submitted for publication by Dr. Rodney 

 H. True, Physiologist in Charge. 



For many years there has been more or less confusion among crude- 

 drug dealers in regard to what plant should be considered the true 

 medicinal " Dioscorea." Although there is little real evidence that 

 our native species of Dioscorea differ much in their medicinal quali- 

 ties, some authors have expressed a marked preference for a rhizome 

 which is now very rare in the trade. It is here shown that there is 

 better historical precedent for the use of the rhizome now handled by 

 crude-drug dealers than for the form which of late has been preferred. 



In carrying out this investigation Mr. Bartlett has found it neces- 

 sary to consult much material located in many herbaria, collections, 

 and museums. He was assisted very materially by drug specimens or 

 information furnished by Mr. Floyd Cole (Trade, Tenn.), Mr. H. E. 

 Ellis (St. Petersburg, Fla.). J. Q. McGuire & Co.' (Asheville, N. C), 

 Mr. Joseph Powell (Bristol, Tenn), Mr. E. W. Proctor (Cincinnati, 

 Ohio), and Vannoy & McXeill (North Wilkesboro, N. C). To the 

 following persons he is indebted for the use of herbarium specimens or 

 notes on geographic distribution: Mr. W. H. Aiken (Lloyd Library), 

 Prof. S. M. Bain (University of Tennessee), Mr. H. W. Barre (South 

 Carolina Agricultural Experiment Station), Mr. C. D. Beadle (Bilt- 

 more Herbarium), Prof. W, J. Beal (Michigan State Agricultural 

 College), Mr. Stewardson Brown (Philadelphia Academy of Natural 

 Sciences), Prof. W. A. Buckhout (Pennsylvania State College), Mr. 

 George H. Chapman (Massachusetts Agricultural Experiment Sta- 

 tion), Prof. Mel. T. Cook (Agricultural Experiment Station, Dela- 



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