158 GARDENING FOR THE SOUTH. 



Should there be a break at any other point, this pro- 

 vides a suitable poiut for the attack of the disease. 

 The roots are more or less cut or bruised in harvesting, 

 and these places favor the entrance of the fungus. As 

 the mould advances within the tissue of the plant it 

 exudes a substance which is very active in causing the 

 starch in the potato to dissolve, as also the walls of the 

 cells to become partially decomposed. In this way the 

 juice from the decaying sweet potato is able to induce 

 a similar decay in healthy roots. 



It is quite safe to assume that the mould makes its 

 entrance into the potato from the surrounding medium, 

 and usually after the roots have been harvested. It does 

 not, as far as known, begin by infecting the leaves of the 

 growing plant, and then pass down the stem, as is true 

 with the soft rot of the Irish potato. The fact that it 

 finds broken, bruised or cut spots in the roots favor- 

 able places for entrance suggests the importance of 

 being careful in harvesting and subsequent handling, 

 that the least possible harm shall come to the skin of 

 the roots. It is also true that the soft rot is greatly 

 favored by a moist atmosphere, especially shortly after 

 digging, at the time the roots are undergoing the 

 process known as " sweating." At this critical period 

 it is very necessary that the potatoes be stored in a 

 well-ventilated room, where a constant temperature 

 of not far from seventy degrees, or about that of a living 

 room, may be sustained. All soft potatoes should be 

 sorted from the healthy ones and destroyed. 



Cercospora Apii (Fries.). Celery-leaf blight. The evi- 

 dence of the fungus is the appearance of pale yellow- 

 green spots on both sides of the leaves, about one-fourth 

 of an inch in diameter. These will soon change to a 

 brown color with a lighter colored center, and, if per- 



