88 THE BANANA 



wrinkles appear in the sheath (trunk) and midrib of the 

 leaves, wh ch gradually dry up, and finally the trunk 

 bends down along a line of least resistance. As soon as 

 the disease becomes evident, the bulb when cut shows 

 signs of putrefaction. Its whitish colour has turned 

 yellowish with reddish-brown spots or streaks. The roots 

 do not begin to decay before the tissue at their base is 

 affected, proving that the germ does not enter by them. 

 Essed has traced the starting-point of disintegration to an 

 old wound-surface, and he says that there is " reason to 

 assume that the fungus at the start behaves as a wound 

 parasite or saprophyte, living at first on the exudation, 

 and by degrees making its way up into the damaged 

 vessels." 



The disease is caused by a previously undescribed 

 fungus, which the author proposes to call Ustilaginoidella 

 musceperda. 



The fungus at first attacks the fibro-vascular bundles, 

 preventing the passage of water along the wood vessels, 

 which explains the water-starved appearance of the plant, 

 and then spreads outwards, forming numerous spores of 

 more than one kind. 



In the rhizome (bulb) of a diseased plant the fungus is 

 found chiefly in the wood vessels and adjoining tissue ; 

 the vessels become discoloured and the sap is absorbed 

 by the fungus in them. The first change in the parenchyma 

 is an unusual cloudiness of the protoplasm, apparently 

 caused by an enzyme secreted by the fungus ; the brown 

 discoloration and the slimy degeneration of the walls of 

 the vessels must also be ascribed to an enzyme. Gradually 

 the cell contents are absorbed and replaced by the carti- 

 laginous sclerotium. Transverse sections of the leaf -blade 

 show that the hyphae in the vessels send out branches at 

 right angles to the walls ; these end in the intercellular 

 spaces among the subepidermal cells and produce oblong 

 or irregular sclerotia. In the sheath special sclerotia are 

 formed in the star-shaped parenchyma cells : the hyphae 

 which enter these cells send branches into the rays, 



