356 



The Sderotiiiias ni'e chanicteiizcd diu-iiig the vegetative stage by the 

 formation of sclerotia. Tlie sclerotia are wliite when first formed, but 

 soon tlie outer celluhir layers become blaciv and more or less roughened. 

 These sclerotia are usually formed abundantly on the diseased root, es- 

 pecially during tlie later stages, thus affording an easy means of dis- 

 tinguishing these diseases. 



There are two distinct types of Sclerotinial diseases of ginseng ; one 

 In which the entire root becomes black and covered with hard black 

 sclerotia and the otlier in which the root retains its natural color, but in 

 v.'hich a number of blark sclerotia are developed on the outside. The 

 fcu'iner type is known as Black Rot and is familiar enough in those gar- 

 dens infested by it. The diseases of the latter tyi>e have collectively gone 

 under the name Grown Rot, although it is by no means certain that the 

 various diseases given this name have all been caused by the same or- 

 ganism. 



It was with the object of determining the name and characteristics of 

 each organism connected with these diseases and of finding some means 

 for successfully combating them that the present investigation was under- 

 taken. The work during the summer of 1910 was carried on at Cornell 

 University under the direction of Prof. II. II. Whetzel, to whom grateful 

 acknowledgments are due for the use of his private notes collected during 

 his work on ginseng diseases. The work was continued during tlie past 

 winter in the laboratories of the Botanical Department of Wabash Col- 

 lege under the direction of Prof. M. B. Thomas. 



BLACK ROT. 



The first recorded mention of this disease was by Van Hook ('04) 

 from a ginseng garden in New York. However, witli the increased culti- 

 vation of ginseng it has spread, until last sununer it was reported not only 

 from several counties in New York but from other States as well. While 

 to the author's knowledge, its destruction has been extensive in only a 

 few cases, it is well worth while to be on the lookout for it, as this dis- 

 ease is very difficult to eradicate when once it obtains a foothold. 



Roots attackt'd liy P.lack Rot are coal blaik in color when dug. chang- 

 ing to a dirty m'liy when dried. 'I'licx arc (lc\oid of all llicir small librous 



('04) Van Hook, J. -Af. Diseases of Oiusoii^'. New York (Coniolli .\;,'r. K.vp. 

 Sta. Bui. 219: 1. c. 181-1S12. 1004. 



