Fern Diseases 257 



ever, with regard to the zoospores. As worked out 

 by Atkinson* the zoospores in P. intermedins arc 

 broadly fusoid, with pointed ends, and terminating 

 at each end in a long cilium. After moving about 

 for five to ten minutes, it gradually comes to a rest, 

 the body undergoing plastic movement until the 

 organism is cut into two parts, forming now two 

 zoospores oval in form and each with a cilium at- 

 tached directly at the smaller end. This peculiarity 

 makes this organism diflferent from Pythium de 

 Baryanum. For control method soil sterilization is 

 recommended (see pp. 32-43). 



COMPLETORIA DAMPING OfF 



Caused by Cotnpletoria complens Lohde. 



Symptoms. The disease attacks yoimg fern pro- 

 thallia. It is manifested as a yellowish or yellowish- 

 brown color of the prothallia as they lay on the soil 

 in the bed or pot. A careful examination will show 

 that the prothallia are spotted, the spots varying 

 from yellowish-green to yellowish-brown, changing 

 to deep brown and to black. In an advanced stage, 

 a prothallium will present a checkered or mosaic 

 appearance. As rot sets in, the prothallium becomes 

 ragged and torn. 



The Organism. The causal organism was studied 

 by Atkinson.t The mycelium of the fungus is made 



•Atkinson, G. F., New York (Cornell) Agr. Expt Su. Bui. 94: 

 247-250, 1895. 

 t Ibid., 252-260^ 1895. 



