REPORT OF THE SOCIETY 59^ 



AN ALTERNARIA DISEASE OF POLYPODIUM 

 By T. G. Major, B.S.A., M.Sc. 



During the past winter the attention of the writer was drawn to a spot 

 disease occurring on a fern (Poly podium sp.) in the experimental greenhouse at 

 Macdonald College. The disease appeared to be spreading very rapidly and 

 was ruining the plant from the decorative point of view. Since it was the only 

 specimen of its kind in the greenhouse it was determined to carry out some 

 experiments to ascertain the cause of the disease. The results of these exper- 

 iments show that the causal organism is an Alternaria. The writer has not been 

 able to find an}^ reference in the literature to an Alternaria disease of Polypo- 

 dium. 



An Alternaria disease of Polypodium. 

 Symptoms 



The lesions occur mainly on the fronds but some maj'' also be found on the 

 stems. They are of the typical Alternaria kind, brown in colour, circular to 

 elliptic, of various sizes, occurring singly or in groups, concentrically zonate with 

 age, irregularl}' scattered over the surfaces of the fronds, but mostly at the edges 

 and tips. This last condition is probably due to the fact that the water tends 

 to gather at the edges and serves as a favourable medium for the germination of 

 the spores of the fungus. 



