GLOEOSPORIUM 435 



numerous. The spores are almost cylindrical, 14-20 x 2-2-5 /*i 

 and are ejected in slender tendrils mixed with mucus. 



Spray with potassium sulphide on the first appearance of 

 the disease. Bordeaux mixture may be used if already pre- 

 pared for other purposes, but it must be much diluted if the 

 foliage is young, otherwise it will be scorched. 



Rhododendron leaf blotch (Gloeosporium rhododendri, 

 Briozi and Cavara) sometimes forms large, irregular, 

 yellowish blotches on the leaves of different kinds of 

 Rhododendron. The blotches are often zoned, spore-clusters 

 black, shining, grouped in concentric lines ; spores cylindric- 

 oblong, 15-20X4-5 p. 



The most practical way of arresting the disease is to collect 

 and burn infected leaves. 



Grape rot. This disease, caused by Gloeosporium ampelo- 

 phagum (Sacc.), has proved a veritable scourge in European 

 vineyards, and is much more prevalent on vines grown in the 

 open air than when under glass. It has also caused serious 

 injury to vines in the United States since 1884, an d was pro- 

 bably introduced to that country from Europe. In Britain this 

 disease occurs now and again in vineries, but as comparatively 

 few vines are attacked in one locality, its spread is not to be 

 feared if prompt measures are resorted to. The general 

 symptoms of the disease are the presence of numerous 

 blackish spots, which eventually form small wounds at the 

 parts attacked. These spots occur on the leaves, young 

 shoots, tendrils, and fruit. Young green shoots only are 

 attacked. The points of infection are at first minute and 

 brownish ; these gradually increase in size and often run into 

 each other, forming large wounds, which eat through the 

 bark into the wood, sometimes extending to the pith, and 

 often form large black chinks, causing the branch to become 

 distorted and rough, and black as if scorched. The tendrils 

 are often similarly affected. On the leaves the spots formed 

 by the fungus are irregular in outline, greyish and bordered 

 by a darker line. Eventually the tissue of the diseased 

 patches becomes dry and dead, and falls away, leaving holes 

 in the leaf. The leaf stalks are often distorted in various 

 ways by the fungus. In many instances the flower stalk is 

 attacked when the flowers are opening, and in such cases the 

 whole inflorescence is killed at once. When the grapes are 

 more or less grown before they are attacked, the diseased 



