Damping Off. 323 



A Potting Bed Fungus New to America. 

 Complctoria Comjjlens Loh.de. 



This is an organism which is parasitic upon fern prothallia grown 

 in forcing houses. It has been known in Europe for several years, 

 but was first found in this country during the winter of 1893-4, in 

 the botanical conservatories of Cornell University, while studying 

 the rotting of prothallia induced by Artorogus intermedins (de 

 Bary), described in a former paragraph of this paper. Ultimately 

 the prothallia decay, but the first signs of disease when caused by 

 this parasite alone is the appearance of a yellow or yellowish brown 

 color imparted by the prothallia as they lie on the soil of the pot or 

 bed. The prothallia are so small that usually the color appears to 

 reside in the entire prothallium when seen by the unaided eye. 

 When examined by the aid of a microscope, however, unless the 

 prothalhum is in the last stages of the disease, the decay will be 

 seen to be confined to " spots." 



These spots vary in color from a yellowish green to yellowish 

 brown, deep brown and finally blackish, dependent on the phase of 

 the injury to the cell and its contents. At first the injury is con- 

 fined to single cells, either near together or far isolated, on the mar- 

 gin of the prothallium or at any point over its surface. 



When the trouble is well advanced and there are numerous cen- 

 ters of the disease, as frequently hapj^ens, the prothallium will 

 present a checkered or mosaic appearance, the different pieces of 

 the mosaic being colored with the various shades of color detailed 

 above. It also presents at this time quite a ragged appearance, 

 because many of the cells are dead and the disintegration of their 

 contents makes holes in the plant and rifts in its edges. A short 

 note on the occurrence of this fungus in the United States was 

 published by the writer in the Botanical Gazette for No^^ember, 

 1894. It is a very interesting fungus from its very simple struct- 

 ure, its peculiar form, mode of development, and as a plant parasite, 

 from its being a member of the Entomojphthoreae, which are almost 

 entirely parasites of insects. 



The vegetative body of the fungus is a more or less compact, 

 grape like, botryose cluster of oval or curved hyphal branches 

 originating from a common center, and presenting on the surface 

 a series of convolutions formed by the external hyphal branches 

 lying close together over the surface. This vegetative body lies 



