DAMPING OFF. 265 



DAMPING OFF BY A STERILE FUNGUS. 



Much of the trouble in the nature of damping off both in the 

 forcing house and in the fields is caused by a fungus which has 

 been under study at several different times during the last three 

 years, but up to the present time has refused all the encourage- 

 ment, which it has been possible from present experience to offer 

 it with the hope of inducing it to develop some characteristic 

 fruiting organs in order that its real nature and affinities might 

 thus be made known. There are quite characteristic features of 

 the mycelium and of certain sclerotoid bodies developed on the 

 mycelium, and which with a little care serve to distinguish it from 

 other known fungi. 



I first observed it while studying the diseases of the cotton plant. 

 (See Bull, Ala. Agr. Exp. Station, Dec. 1892,) In the cotton 

 growing states it is a very frequent parasite on young cotton plants 

 and produces a very large percentage, so far as my observation 

 has gone, of what is known as " sore shin " in that section. The 

 trouble is caused by the fungus growing first in the superficial 

 tissues of the stem near the ground and disintegrating them before 

 it passes to the deeper tissues, in other words the fungus never 

 seems to penetrate far in the living tissues but " kills as it goes " 

 and the tissues become brown, depressed and present the ap- 

 pearance of the plant having a deep and ugly ulcer at the surface 

 of the ground. The fungus does not spread into the tissues either 

 above or below the ulcer to any extent, but literally eats away at 

 that point until it has severed the stem at the affected place or the 

 plant has recovered from its effects. The plants do not seem to 

 suffer seriously from the disease until the woody portion contain- 

 ing the vascular bundles is nearly or quite eaten away. 



In the latter case all communication between the root and the 

 aerial portion of the plants is cut off and of course the plant withers 

 and dies. But frequently the stem may be eaten off so far that 

 the plant has not sufficient strength in the remaining tissue at 

 that point to support it and it will fall over, and perhaps if the 

 disease does not progress any farther it may remain fresh and 

 green for weeks, but it is rare that after this stage the plant re- 

 covers sufficient strength at that point to erect itself again. 

 Frequently however when the stem is nearly eaten off the disease 

 may be arrested and the plant completely recover from the effects. 



