246 DISEASES OF TROPICAL PLANTS OH. 



wood, primings, etc., if allowed to remain on the ground, 

 form suitable places for the fungus to grow and fruit, 

 and thus aid the spread and perpetuation of the disease. 



The Leaf Spot (Septogloeum mori, (Lev.) Briosi and 

 Cavara) occurs also in Europe, where it is sometimes 

 called rust. It occurs chiefly on the younger leaves, 

 where it produces angular spots, pale -brown in the 

 centre and surrounded by dark reddish brown bands. 

 These spots may be J inch in diameter. On the upper 

 surface are little raised pustules. In moist weather 

 these pustules swell into rounded, pale-coloured blisters, 

 which contain numerous spores. The leaves drop, and 

 in very moist weather the loss is sometimes 10 per cent 

 of the foliage. The spores are elongated, colourless, 

 rounded at the ends, and segmented by three to five 

 cross walls, usually curved. They germinate readily in 

 water. 



The disease can be controlled readily by the use of 

 Bordeaux where practicable to use it. 



The Mildew of the mulberry (Phyllactinia corylea, 

 (Peri) Karst.) occurs in India, Japan, and Madagascar. 

 It occurs on the under sides of the leaves, and produces 

 the characteristic effect. It is not serious. 



The Mulberry Trunk Rot (Polyporus hispidus, (Bull.) 

 Fr.) also occurs on the apple, plum, and apricot in 

 Kashmir and many other trees in Europe. It is a 

 wound parasite which attacks the trunk and large 

 branches, causing the heart wood to undergo decay and 

 become soft, spongy, and yellowish-white. In discussing 

 this disease, Butler says : 



Separating the outer healthy layers of young wood from 

 the rotten central portion is a hard brown zone, consisting of 

 cells filled with a brown gummy matter; in this the parasite 

 takes its main development. It is nourished in the brown zone 

 mainly by the cell contents, while the walls are at first left 

 unaltered. Only at a later period, when the cell contents are 

 exhausted, is the wall crowded and the wood itself softened. 



The diseased branches usually die, but the trunk 

 may become hollow, due to the decay of the heart 



