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XIV. 



CHRYSOPHLYCTIS ENDOBIOTICA, Scliilb. (Potato-wart or 

 Black Scab), AND OTHER CHYTEIDIAOE^. 



By T. JOHNSON, D.Sc, F.L.S., 

 Professor of Botany in tlie Eoyal College of Science, Dublin. 



(Plates IX.-XI.) 



[Read March 23. Ordered for Publication April 6. Published June 1G, 1909.] 



My attention was first called to tlie warty disease of potatoes by an article 

 in the Journal of the Board of Agriculture (England), entitled, "Anew Potato 

 Disease, Chrysophlyctis endohiotica, Sehilberszky," from the pen of Professor 

 M. C. Potter (1), who, in the beginning of 1903, sent me some spore material. 

 Later in the year, through the late Dr. Maxwell Masters of the Gardeners' 

 Chronicle, I got a quantity of warty tubers from Cheshire, from Mr. New- 

 stead, the Curator of the Grosvenor Museum, Chester. I naturally watclied 

 with interest the spread of the disease through Great Britain, and its 

 continued non-appearance in Ireland. 



Attention in Ireland had been called in 1907 to the dangerous character 

 of the disease, by the publication of an illustrated leaflet by the Department 

 of Agriculture and Technical Instruction for Ireland (2), and early in 1908 

 by the issue of an Order in Council, giving power to penalize anyone found 

 importing or concealing cases of the disease. Hundreds of samples of scabby 

 potatoes were in consequence sent in for repoi't ; but they proved to be either 

 the ordinary scab or Spougospora scab. In October, 1908, however, by the 

 discovery of three cases of warty tubers in Co. Down, Ireland's clean record 

 was lost. 



Steps were immediately taken by the Department to stamp out the 

 disease, it need hardly be said. At the end of October, I received from it some 

 of the warty tubers (PI. IX., fig. 1). Examination of the haulms or "potato- 

 tops" of the diseased plants showed that the trouble was not confined to 

 the tubers, but affected also the branching underground stem (the stolons), 

 and even the fibrous roots. This is in harmony with the observations of 

 Borthwick (3) in Scotland, and of Salmon (4) in Kent, who give excellent 



SCIENT. PROC, K.D.S., VOL. XII., NO. XIV. Z 



