DA MPIN G - OFF. 



349 



falls over. In many cases, the top of the plant may re- 

 main alive and fresh for some days after it has fallen 

 over. 



It is commonly supposed that damping-oft is due to a 



Fig. 6 



Fig. 3. 



fungus. The fungus which has been called the "pot- 

 ting-bed fungus" in Europe is commonly supposed to 

 cause the difficulty, but the subject is little understood 



in this country. It is by no means certain that all 

 damping-off is the same. It is possible that two or 

 three distinct troubles are called by the same name. 

 Damping-oft is most troublesome under glass and 

 among plants which are crowded, but it may occur in 

 the nursery-row out of doors. Certain conditions of 

 atmosphere and culture induce the attack of the fungus. 

 In my experience and observation, a soil dry beneath 

 and wet on top afiords the best conditions for damping- 

 off. It is a common fault to merely sprinkle the propa- 

 gating bed, allowing the under soil to remain dry and 

 powdery. The operator may suppose that he has given 

 enough water to wet the soil throughout. This condi- 

 tions of affairs is particularly apt to occur when water is 

 applied from a hose, for I find that there is then a ten- 

 dency to apply too little rather than too much. The 

 amount of water can be guaged more readily if applied 

 from a pot. 



There is little to be done in the way of a remedy for 

 damping-off', for unless the plants are particularly valua- 

 ble it will scarcely pay to attempt to save them after 

 they are attacked. But preventives can be employed. 

 Keep the plants stocky, never allow them to crowd, 

 give plenty of air, and endeavor to keep the soil uni- 

 formly moist throughout. 



From Professor A. B. Seymour, lldi vard Univer- 

 sity. — In his " Enumeration of the Peronosporea: of the 

 United States," Professor Farlow says: "In this coun- 

 try the species of pythium have not been sufficiently 

 studied, and no mention is made of them in this Daper, 

 although they possess a decided agricultural interest, 

 since one species apparently causes what is known in 

 some parts of the eastern states as the potting-bed fun- 

 gus, which is very destructive to young house plants in 

 the winter. Other species are known in decaying plants 

 in damp ground." This is the extent of our knowledge 

 of the subject in this country. In Europe there are 

 several species of interest in this connection.* 



In 1878 DeBary observed plants of CIl'oiuc ^'iolaira 

 which turned brown near the surface of the ground and 

 also in spots on the stem and leaves. The plants wilted 

 and became foul or dried up. The next year they were 

 worse and several additional species of flowering plants 

 were attacked. All the discolored tissues were found to 

 contain mycelium, sometimes of several kinds, but only 

 one kind was present in every case and that was Phytopli- 

 llioi-a oiiinivora (or Pvlliiuin oiiuii't'ora), a species closely 

 allied to the potato rot fungus. Conidia-bearing 

 branches of the mycelium (Fig. i) grow out through the 

 epidermis and the conidia germinate by forming zo- 

 ospores (Fig. 2). The resting spores (Fig. 3; correspond 

 to those of the grape mildew. I do not understand that 

 this fungus lives in the soil. 



Pythium is a fungus allied to phy tophthora, but appar- 

 ently lower in rank, Pytliiiini 7u:\ii/is was found by De- 

 Bary growing on potato tubers which had already been 

 partly rotted by the common potato rot fungus, Phytofh- 

 thora infestaiis. He found that the pythium would 



*Bop. Gaz., 1883. 



