Fern Diseases 257 



ever, with regard to the zoospores. As worked out 

 by Atkinson* the zoospores in P. intermedius are 

 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 different from Pythium de 

 Baryanum, For control method soil sterilization is* 

 recommended (see pp. 32-43). 



COMPLETORIA DAMPING OfF 



Caused by Completoria com pi ens Lohde. 



Symptoms. The disease attacks young fern pro- 

 thaliia. 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.! The mycelium of the fungus is made 



♦Atkinson, G. F., New York (Cornell) Agr. Expt. Sta. Bui. 94: 

 347-250, 1895. 



t Ibid., 252-260, 1895. 



