RHODODENDRON GALLS 167 



fungus probably belongs to the category known as root- 

 parasites, travelling in the soil by means of mycelial strands 

 or rhizomorphs. 



Tanaka, Journ. Coll. Sci. Imp. Univ. Japan, vol. iv. pt. i, 

 p. 193, pi. xxiv.-xxvii. (1891). 



BASIDIOMYCETES 



THELEPHOKACEAE 



RHODODENDRON GALLS 

 (Exobasidium rhododendri, Cram.) 



The presence of this fungus is indicated by the occur- 

 rence of gall-like swellings on the leaves of Rhododendron 

 hirsutum and R. ferrugineum. The galls vary in size from 

 that of a pea to a marble, are at first of a pale yellowish- 

 green colour, becoming red on the side exposed to sun- 

 light. During the summer the entire surface of the galls 

 becomes covered with a very delicate bloom, due to the 

 presence of basidia, or spore-bearing organs. The my- 

 celium of the fungus remains in the tissues of the gall. 



PREVENTIVE MEANS. Collect and burn diseased leaves 

 before the fruit of the fungus is produced. I have observed 

 that when infested leaves have been removed sufficiently 

 early, the disease does not appear the following year on 

 the same plant ; hence probably there is no permanent 

 mycelium in the tissues, and the only means of infection 

 is by spores. , 



Several other species of Exobasidium form galls on 

 plants belonging to the following genera : Rhododendron, 



