Damping Off. 



" Damping off" is a disease of seedling plants whicli rots or disin- 

 tegrates the tissues at tlie surface of the ground. The tissues thus 

 changed weaken, lose their firmness and supporting power, and the 

 seedling falls prostrate on the soiL The disease is wide spread and 

 sometimes very common. It occurs not only in gardens and fields 

 but is a very frequent attendant upon the culture of seedling plants 

 in the forcing house or bed. The trouble is favor'ed by damp soil, 

 comparatively high temperatures, and humid atmosphere. 



The term " damping off " is therefore indicative of one of the 

 attendant conditions of the soil inducing the disease. While this 

 popular expression is thus far significant of the trouble it is by no 

 means the exact statement of the case. The plants do not damp 

 oft" because of the abundant damp or moisture in the soil. The 

 dampness encourages the growth of minute parasitic plants, not 

 visible to the unaided eye, which pierce the seedling, feed upon 

 its substance and set up disintegration processes which result in 

 the death and collapse of the affected parts. Soon after the plant 

 falls the dissolution of the tissues near the surface of the ground 

 has usually proceeded so far that communication by the ordinary 

 physiological processes of life is cut off, and the plant then with- 

 ers and dies. While damping off is due to the action of minute 

 fungus parasites, it is by no means caused by one and the same 

 species. Different species of fungi may under some conditions 

 produce nearly or quite identical phenomena in the progress and 



Frontispiece. — This is from a photograph of an experiment to show the 

 parasitic uature of the Artotrogus debaryauus (Hesse). Before planting the 

 cucumber seed the pots were filled with soil which was thoroughly wetted and 

 then steamed in the steam sterilizer tor several hours on three successive days 

 in order to kill all the orgauisms. The seed was then planted and wheu just 

 coming up some plaut tissue with freshly developed stages of the fungus waa 

 placed by the seedlings in pots 5, 6 and 8, while pot 7 was left as a check. The 

 result can be easily seen in the photograph, the check plants remainiug unharmed 

 while all the plants in 6 are killed and only one remains healthy in each 

 of 5 and 8. 



