DAMPING OFF. 235 



in the seed bed or forcing pots of our gardens and hot houses, 

 especially if undue moisture is present in the soil. In the gardens 

 it is frequently impossible to control the amount of moisture in the 

 soil, and in the forcing house where often the light is defective, 

 the air is not fresh or it is supercharged with moisture, it is often 

 nearly or quite impossible by the ordinary methods to preserve 

 that equilibrium of environment which will permit the growth of 

 the seedling and at the same time check the growth of its inimical 

 guest. 



All experienced gardeners are probably familiar with the appear- 

 ance of the diseased seedling when affected with the damping off 

 fungus. At this day when the germ theory of disease, both animal 

 and plant, has so completely poisoned the minds of all classes of 

 people there is little difficulty in successfully advocating what is 

 now an established fact, that the damping off fungus is a parasite 

 in the seedlings and invades the tissue of the latter for the pur- 

 pose of obtaining its food. It is fortunate therefore that especial 

 attention can be given to setting forth the facts in the structure 

 and development, and other peculiarities of the parasite, which 

 are quite important to know in order to properly treat it, and also 

 because it can then be distinguished from others either near or 

 remotely related, some of which induce diseases in the early 

 life of certain ferns or fern-like plants and cannot disease 

 seedlings. 



The first striking pecularity in a bed or pot of seedlings affected 

 with the disease which attracts our attention is the prostrate con- 

 dition of a few plants while others are upright and apparently 

 healthy. The prostrate plants are found to be shrunken at or 

 near the crown, i. e. near the root or the surface of the ground. 

 Frequently when our attention is thus first called to the disease 

 the collapsed tissue of some of the prostrate plants is so far dis- 

 integrated as to be in a soft and rotted condition, so that on pull- 

 ing at the plant it breaks easily at this point. Farther investiga- 

 tion will show that usually the entire root system is by this time 

 decayed, while the greater part of the stem above ground and the 

 young leaves are still green and possibly quite fresh, or flabby, or 

 more or less wilted. 



