322 



A New Potato Disease. 



the approach of autumn each plasmodium is surrounded by a 

 very hard and firm, brown cell-wall and forms a resting-spore 

 (Fig. 3). The resting-spores are most frequently found in the 

 external layer of cells, but in many cases may be observed many 

 layers deep in the tissues. 



This potato disease is apparently the same as that which has 

 been noted by Schilberszky,* from Upper Hungary. He 

 describes potatoes with dark-coloured pustules, irregularly 

 grouped and crowded together, forming wart-like outgrowths, 

 and with a parasitic organism present in the periderm. This 

 fungus belongs to the order CJiytridinex, and has been named by 

 Schilberszky Chrysophlyctis endobiotica. He distinguishes two 

 kinds of reproductive cells, swarm-sporangia and resting-spor- 

 angia. The swarm-sporangia are of a yellow-brown colour, and 

 are generally found in the sub-epidermal cells, sometimes two or 

 three in one cell. On germination they give rise to small 

 spherical swarm-spores, which penetrate the walls of the neigh- 

 bouring cells and so spread the disease. The germination of 

 the resting-sporangia has not been observed. The internal pro- 

 gress of the disease is indicated by a distinct brown colouring of 

 the tissues, which change of colour affects the whole of the 

 protoplasm, with the exception of the starch-grains, as well as 

 the shrunken cell-wall. Schilberszky considers that this para- 

 site bores its way through the cell-wall and does not enter the 

 plant through a wound. 



At present the disease has only been reported to me from 

 Cheshire, and possibly it may have escaped notice in other 

 localities. How it has been introduced into England I have not 

 been able to ascertain, but, from my observations, it is evidently 

 a very destructive parasite, which possesses most effective means 

 of spreading itself if only opportunity offers. As, so far, it 

 appears to be of local occurrence, it is of the highest importance 

 to stamp it out before it obtains a firm foothold in this country. 

 This might be done by carefully sorting the potatoes and 

 destroying those attacked. These should in no case be allowed 

 to pass out of an infected district or be used for " seed." It is 



* " Ein neuer Schorfparasit der Kartoffelknollen. " Berichte d. Deut. Bot. Gesell. 

 Bd. XIV., 1896. 



