Damping Off. 305 



or quite impossible by the ordinary methods to preserve that equi- 

 librium of environment which will permit the growth of the seed- 

 ling 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 difhculty 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 purpose of 

 obtaining its food. It is fortunate, therefore, that especial attention 

 can be given to setting forth the facts in the structure and develop- 

 ment, and other peculiarities of the parasite, which are quite import- 

 ant 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 can not 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. Fre- 

 quently when our attention is thus first called to the disease the 

 collapsed tissue of some of the prostrate plants is so far disintegrated 

 as to be in a soft and rotted condition, so that on pulling at the 

 plant it breaks easily at this point. Farther investigation 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. 



The conditions of the aerial portions of the plant at this early 

 stage of its fall are largely dependent upon the moisture content of 

 the atmosphere. If the moisture be quite dry the seedling will be 

 quite flabb}^ before it falls and will soon wilt thereafter, but if the 

 moisture content is large the tissue will remain quite firm for a time 

 unless the soil upon which it is lying is so saturated with moisture 

 as to encourage the rapid growth of the fungus in the prostrate 

 portion of the plant. When this is the case the entire plant soon 

 becomes a putrid mass and the tissues often take on a dark color. 



After attention has been called to the trouble by the preliminary 

 collapse of a few plants, if others are carefully noted some will 



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