DAMPING OFF. 253 



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

 published by the writer in the Botanical Gazette for November, 

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

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

 site, from its being a member of the Entomophthoreae, which are 

 almost entirely parasites of insects. 



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

 grape like, or 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 

 within a single cell of the prothallium, sometimes completely fill- 

 ing even quite large cells, while at other times the body may be 

 smaller especially in smaller cells of the prothallium, where it 

 sometimes consists of only a few hyphal branches closely curved 

 upon their parent cells. These hyphal branches vary from 7 ^ to 

 15 //. in diameter or may even be of a greater diameter, and are 

 one and one-half to two times longer. When the plant body in a 

 single cell becomes mature it may spread to the surrounding cells 

 by certain of the external hyphal branches putting out a slender 

 germ tube which pierces the adjacent intervening wall. This is 

 done by the tube of the hypha excreting a substance which dis- 

 solves the cellulose of the wall making a small minute pore and 

 at the same time turning the adjacent portions of the wall brown 

 in color. The wall of the slender thread which squeezes its way 

 through this opening is also colored brown, and this color is fre- 

 quently extended to the slender portion of the thread or tube, in 

 which the protoplasm passes or migrates to the center of the cell 

 as shown in figure 44. 



When it has reached the center of the cell lumen the free end 

 enlarges and forms a rotund body which finally becomes oval. 

 At this time it is about 15^ to 25^ in diameter, with quite coarse- 

 ly granular protoplasm and with one or more large vacuoles. By 

 this time also all of the protoplasm from the original cell has 

 moved into this oval body in the center of the cell, leaving behind 

 only the wall of the slender tube by which it gained entrance and 

 which is still connected with the wall of the living organism. 

 This old wall as well as the wall of the prothallial cell where the 

 organism entered becomes brown in color soon after the proto- 



