402 DISEASES OF CULTIVATED PLANTS 



less of a stroma is present on the surface of the host, from 

 which the basidia spring. 



Widely diffused in Victoria, Australia, on the vine. 



Var. album (Montem). A variety founded on the whitish 

 colour of the fruiting stage of the fungus. In the typical 

 form this is yellowish, and the mycelium is clear yellow just 

 under the skin of the fruit. 



On leaves and fruit-stalks of the vine in Austria. 



Blister blight of tea plant is due to Exobasidium vexans 

 (Massee). This disease is described by Dr. (now Sir George) 

 Watt, as ' one of the very worst blights on tea. Is known to 

 the planters as blister blight. I have seen hundreds of 

 acres completely ruined by it.' The foliage is the part 

 principally attacked, although young shoots are also some- 

 times infected. On the leaf the first indication of infection 

 is the appearance of a small pink spot, which gradually 

 increases in size. At this point the upper surface of the leaf 

 becomes depressed, forming a rounded pit. A corresponding 

 bulging out is present at the same point on the under surface 

 of the leaf; several such pits may be present on a leaf. 

 Eventually the convex surface of the blister becomes covered 

 with the fruit of the fungus, under the form of a very delicate 

 velvety pile. Conidia are first produced, followed by 

 lusidiospores borne on basidia. 



Conidia produced on slender conidiophores before, or 

 mixed with the basidiospores, i -septate, slightly constricted, 

 fusiform, 14-16x5-6 p. basidia cylindrical, bearing two 

 sterigmata, spores ovate-oblong, continuous, hyaline, 5 X 3 /*. 



Dr. Watt states that the disease invariably appears on tea 

 that has not been pruned in the autumn, and about April 

 it extends to pruned tea, which has by then come into leaf. 

 This statement suggests, unless there is some very strong 

 reason to the contrary, that where the disease is prevalent, 

 autumn pruning should be practised. 



Massee, Kew Bulletin, 1898, p. 109. 



Watt, The Pests and Blights of the Tea Plant, p. 419. 



Exobasidium lauri (Geyl.) causes branched, antler-like 

 outgrowths, two or three feet in length, to spring from the 

 Leaves of Laurus uobilis, and L. canariensis in Italy and the 

 Canary Islands. 



Exobasidium andromedae (Peck.) causes similar features 



