DISEASES OF GINSENG. 83 



roots the black (Fig. 33) appearance. At this stage the root ia 

 tough and very pliable. Within, it is still the natural color and 

 instead of being compact and brittle, it is soft and watery. There 

 is no offensive odor accompanying this rot as is the case with the 

 soft rot, but the characteristic taste of the root is lost, it is some- 

 what bitter. Infected roots which have been lying in the soil two 

 or three years gradually become black throughout, soften and 

 finally decay. 



The fungus causing this troulale is one of the cup fungi and 

 belongs to the genus ScleTotinia,. Just recently the cup or spring 

 stage (Fig. 34) has been found. The cup-like Ijody bears the 

 spores of the fungus in great abundance on the upper surface. 

 The spores are shot up into the air and are disseminated hy the 

 wind to different parts of the garden, where they germinate and 

 reinfect other ginseng roots. 



It is probable that the spread of the disease in the gardens 

 is due largely, however, to the abundance of the mycelium of the 

 fungus which ramifies through the soil. The lumps or protuber- 

 ances on the affected root are sclerotia, or hard, tuber-like bodies 

 of compact mycelium. These sclerotia are resistant masses of the 

 fungus mycelium which are capable of carrying the fungus over 

 from year to year. The cells that make up the sclerotium germi- 

 nate and send out germ tubes just as does a spore. 



The peculiar thing about this disease is that the period of 

 attack of the fungus on the roots is during cold weather. Roots 

 with well formed buds, when set in the fall in infected soil, do not 

 come up in the spring and the blackening of the root may by this 

 time extend about a quarter (Fig. 35) of the way to the center. 

 There is no spread of the disease after the plants come up in the 

 spring, from the fact that the fungus will only grow at a low tem- 

 perature. In working with the disease in pure culture in the 



