176 DISEASES OF TROPICAL PLANTS OH. 



M. rotalis, another of these horse-hair blights, occurs 

 on tea, nutmeg, and cocoa (see page 65). 



Darjeeling Stem Blight. This disease, which is very 

 imperfectly understood, is referred to by Watt and Mann 

 as follows : 



In the higher parts of the Darjeeling district there will be 

 noticed in almost every garden, a number of bushes dying 

 from the centre, apparently without reason. It has never been 

 noticed below 4000 feet, and appears often in isolated bushes 

 all over the property. In some gardens it is one of the most 

 serious blights on the place. On cutting one of the stems 

 which is dying the centre of the wood appears to be turning 

 black, and this appearance, we are informed by Dr. Butler, is 

 due to a fungus attacking the stem. It demands much more 

 investigation, however, before it can be named, or a remedy 

 recommended with any certainty. In the meantime, all that 

 can be done is to cut out the stems affected below the part 

 discoloured, and paint the stump with Stockholm tar. This 

 is one of the blights which most urgently demand further 

 investigation. 



Internal Stem Disease. This disease has been reported 

 from India, and has been described by Fetch under the 

 name of Massaria theicola. The disease may cause the 

 death of a part or of the entire tree, and may be very 

 slow or very rapid. The diseased plants have very 

 much the appearance of suffering from drought. The 

 fungus usually attacks the tree some distance above the 

 ground, and may work both upward and downward. It 

 is very probable that it enters the host plants through 

 wounds. It is strictly an internal parasite, does not 

 attack the roots, does not cause a decay of the wood, 

 and is most severe in dry weather. Fetch's description 

 is as follows : 



If the bark over this discoloured wood is lightly scraped, 

 it will be found to be quite black internally, and if very thin 

 layers are cut off, minute white circular patches may be detected 

 with the help of a hand-lens. These white patches are the 

 contents of the perithecia, the fructification of the fungus. 



The fungus lives almost entirely in the wood of the bush, 

 only fructification being formed in the bark. The hyphae are 



