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A NEW POTATO DISEASE. 



( Chrysophlyctis endobiotica.) 



In the autumn of 1900 my attention was drawn to some pota- 

 toes presenting a very curiously diseased appearance. At one 

 end were large, irregular tumour-like swellings, very much 

 convoluted, but otherwise not unlike the too-well-known excres- 

 cences of the turnip known as " finger-and-toe," or perhaps more 

 especially that form described as " club " or " anbury." 



These excrescences of the potato-tuber consist of masses of 

 thin-walled parenchymatous cells, very rich in starch. At the 

 periphery of the outgrowths were numerous large, spherical or 

 ellipsoidal resting-spores, measuring jo/jl x 50/4, of a deep brown 

 colour and without any lateral depression (Plate IV., Fig. 3). 

 These spores were always found to be present in great numbers 

 and apparently belonged to some parasite, which set up an 

 irritation stimulating the cells to excessive cell-division and 

 thereby producing the protuberances above described. 



Attempts made to induce these spores to germinate always 

 failed. They were sown in a hanging drop and also upon 

 quite small potato-shoots, under varying conditions and tem- 

 peratures, but hitherto without success. I have, however, been 

 able to infect sound potatoes and exactly reproduce the disease 

 by inoculating the soil with these spores. 



In the spring, three large flower-pots filled with ordinary garden 

 soil were sunk up to the edge in the earth, in the College garden, 

 and potatoes planted in them ; in two of the pots some of 

 these spores were sown in the soil, while the third pot served 

 as a control. The spores had been kept dry in the laboratory 

 during the winter. 



In the control pot the potatoes grown during the summer 

 were perfectly normal. The soil was evidently quite sterile 

 to this parasite, the disease never having been known in this 



