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 



THELEPHORACEAE 



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^ 



