6 WAET DISEASE OF THE POTATO. 



serious loss * * *. All eases of wart disease must be notified to 

 the seoretar}-, board of agriculture and fisheries * * *. In the 

 case of farmers who sell ' seed ' potatoes, notification of the disease 

 is of especial importance, and failure to notify must be regarded as a 

 serious offense * * *. Persons concealing wart disease are liable 

 to prosecution and a penalty of £10." 



PRESENT DISTRIBUTION OF THE DISEASE. 



The disease has been reported from P^ngland (see p. 5), from Scot- 

 land in Perth, Sterling, and Clackmannan counties; from Ireland in 

 Down County; from AVales; from Germany in Westphalia and the 

 Rhine provinces; and from upper Hungary. It has not yet been 

 brought to the United States so far as known, but has already crossed 

 the Atlantic and become prevalent in Newfoundland, where it was 

 lately discovered by Dr. H. T. Giissow, Dominion botanist, who pre- 

 sented a very interesting paper on the subject in December, 1909, 

 before the American Phytopathological Society. Knowing the serious 

 character of the new pest from personal observation of the losses 

 caused in England, he promptly issued a waa'ning bulletin. The 

 Canadian government proposes taking active measures to prevent the 

 further introduction of the disease. Doctor Giissow stated that there 

 have been recent importations of seed potatoes from Newfoundland 

 into the United States. 



NATURE OF THE PARASITE. 



The organism causing the disease is a fungus discovered in 1896 

 in potatoes from upper Hungary by Schilbersky, who named it 

 Clirij802My<Ms enikMotlea and placed it in the lowest group of the 

 ChytridiacefB, Olpidiacete. By others the fungus has been supposed 

 to be OeiJomyces lepro!des. We quote from the excellent description 

 of Prof. T. Johnson, as follows: "The vegetative form consists of a 

 naked mass of protoplasm which may be distinguished in the host 

 cells (just below the epidermis) by being denser, homogeneous, and 

 finely granular. It may be seen abutting on the host protoplasm, 

 and disputing with it, as it devours it, occupation of the enlarging 

 cell cavity. The protoplasm follows and then the cell wall. This, 

 though brown, does not, like the protoplasm and nucleus, disappear. 

 The starch grains are the last attacked and remain white and unin- 

 jured for some time in an invaded cell. The parasitic plasmodium 

 passes from cell to cell by boring its passage through the host cell 

 wall * * *. It is in this stage that it stimulates to active cell 

 division the surrounding host cells and produces the gall or wart." 



ICir. 52] 



