432 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vor.. 2 



seedlings seldom attacked by Pythium have been found to 

 succumb to Rhizoctonia in Louisiana (Edgerton and More- 

 land, '13 ). (5). Alfalfa seedlings have been reported sus- 

 ceptible in one instance (Stewart, French, and Wilson, '08). 

 (6). Seedlings of various species of conifers from a few days 

 to nine weeks old have been reported attacked in several in- 

 stances (Hartley, '12, Clinton, '13). 



The majority of the instances reported above were under 

 normal seed bed or field conditions. Many other cases of the 

 damping off of seedlings might be included where seeds are 

 grown in crowded condition in moist greenhouses. Again, 

 damping off of cuttings by Rhizoctonia is now a well-known 

 phenomenon in the propagating house, and special precau- 

 tions are taken with respect to drainage and moisture in order 

 to reduce the injuries to a minimum. It is safe to assume — 

 since the fungus seems to be found in practically all soils 

 that it is in general the worst enemy of seedling plants. In 

 fact, it may be anticipated that under conditions favorable for 

 the fungus the damping off of seedlings of numerous species 

 may be anticipated. So far as the writer has been able to 

 ascertain there has been no report of the damping off of mon- 

 ocotyledonous plants under normal seed bed conditions. 



While Rhizoctonia Solani may perhaps induce damping off 

 in innumerable species regarding which observations are 

 lacking, some of the host plants which have come to the writ- 

 er's attention as particularly susceptible are the following: 

 lettuce (Lactuca sativa), celery {Apium graveolens), beet 

 {Beta vulgaris), cress (Lepidium sativum), tobacco (Nico- 



tiana Tabacum), balsam (Impatiens balsamina), snapdragon 

 (Antirrhinum ma jus), cotton (Gossypium spp.), cucumber 

 (Cucumis sativus), squash (Cucurbit a spp.), sunflower (Heli- 

 anthus annuus), carrot (Daucus Carota), radish (Raphanus 

 sativus), and phlox (Phlox Drummondii). 



Since the phycomycetous damping off fungus Pythium has 

 been known to pathologists much longer, and prior to 1895 

 was practically the only fungus to which this type of disease 

 was ascribed, it is probable that much damage due to Rhi- 

 octonia has been ascribed to Pythium. Moreover, unless 



