172 DISEASES AND INSECT ENEMIES. 



sides the violet. It undoubtedly is able to live at 

 certain times on decaying organic matter; in fact, 

 it is found in portions of leaves, straw, and other 

 materials occuring in the sand and soil. From 

 the fact that it occurs on bits of decaying leaves 

 it is important to have the propagating sand 

 absolutely free from organic matter. Infection 

 in a great many cases takes place in the propagat- 

 ing bed and soil. The cutting may root readily 

 and to the casual observer may appear sound, but 

 it is infected nevertheless and later on will show 

 the trouble. 



Plants affected with this disease may make a 

 good growth throughout the summer and show no 

 evidence of trouble until September or perhaps 

 October, when they will wilt more or less during 

 the warmer portions of the day and revive during 

 the night. This may go on for a week or more, 

 but finally they wilt completely and die. An exam- 

 ination of such plants shows that the main stem 

 has been practically girdled by the fungus, and 

 that both the water and the food supply have there- 

 by been effectually cut off. The alternate wilting 

 and reviving of the plants is due to the fact that 

 the fungus does its work slowly and thus it requires 

 considerable time to completely encircle the stem. 

 The fact of the matter is, a plant of this kind is 

 probably infected early in its life and for months 

 the fungus slowly grows, gradually destroying 

 cell after cell until finally the plant collapses. 



