66 DISEASES OF GINSENG. 



of blight that he could in any way attribute to diseased seed. 

 Furthermore the disease is not at all common on seedlings, attack- 

 ing them only under very favorable conditions, when there is an 

 epidemic of the disease in older plants in adjoining beds Other 

 diseases of the seedlings are commonly confused with blight. 



Having once been introduced into the garden, the seasonal 

 habits of the parasite are as follows: The fungus passes the winter 

 in old, dead, diseased stems of the previous season, the mycelium 

 remaining alive, but dormant in these old stems, much as the roots 

 of the ginseng lie dormant in the soil. In the spring, when condi- 

 tions become more favorable for the growth of the dormant gin- 

 seng roots and they begin to send up their stalks, the mycelium 

 in the old stems also starts into growth, sending up new spore 

 stalks on which a new crop of spores is quickly produced. The 

 writer has observed this production of spores and has produced 

 the disease in healthy plants by inoculation with them. It is quite 

 possible, that, under favorable conditions, the spores produced in 

 the summer or fall may also pass the winter in a viable condition. 

 They have been germinated freely when placed in water, after hav- 

 ing been kept dry in the laboratory for over three months. On the 

 soil in the beds, most of the spores produced through the summer 

 probably germinate and die by winter. The new crop of spores, 

 produced from the mycelium in the old stems in the spring, are 

 doubtless the chief source of the first, or primary infections. 



The primary infections appear, as I have already described, 

 on growing stems just above the surface of the ground. It is 

 common to find a diseased stalk with the old stems still standing 

 up beside them or lying at their base. It has been found easy to 

 infect the new stalk, as it came through the ground, with spores 

 produced on old stems. The fungus grows rather slowly on the 

 stalk so that the tops are usually well expanded before the spot 



