DISEASES OF THE POTATO. 175 



barrels, in reason, may be used, but we mention three as 

 being a convenient number. Great care must be taken 

 from beginning to end while the poison solution or the 

 dressed potatoes are about. When the last of the solu- 

 tion is done with it should be emptied on to some bare 

 piece of ground or on to the road, but not on to the grass. 



Leaf Curl. In some seasons and districts the leaves 

 of the potato curl and pucker, then turn yellow. This 

 condition is due to a fungus which first gains access to the 

 tubers, and thence to the vessels of the shoots and foliage. 

 Soon after attack the stems turn black and droop, a 

 whitish mould appearing on the dark patches. The tubers, 

 moreover, become "stunted in growth, and although they 

 appear sound when harvested will eventualy rot after stor- 

 age. The particular fungus which causes the foregoing is 

 supposed to be a species of pleospbra. 



Wet Rot. Tubers are sometimes found quite rotten 

 and putrefied, and having a decidely offensive smell. 

 The cause is a bacteria called Clostridiurn, which, says Pro- 

 fessor Marshall Ward, " consumes the cell walls, but 

 leaves the starchy grains intact. " In the February issue of 

 the Board of Agriculture Journal it is stated that " Wet 

 Rot " is due to the action of the fungi of the potato 

 disease (Phytopthora infestans) and of Winter Rot (Nec- 

 tria solani). The spores of the former infect the young 

 tubers before lifting, and the mycelium of the same 

 fungus passes down the stems into the tubers. If the 

 season is wet and warm, the mycelium continues to grow, 

 causing brown spots to appear, and ending in the rotting 

 of the tuber. If the tubers are kept dry the mycelium 

 remains stationary till the following spring, then com- 

 mences growth, passes into the sprouts, and finally ap- 

 pears in the fruiting condition on the leaves. Then the 

 Winter Rot fungus produces softening and swelling of the 

 tubers, which aro later attacked by bacteria, thus show- 

 ing " Wet Rot." 



