182 NEW SUGARCANE DISEASES 



tei'istic discoloration of the pith, <is shown in PI. I, Fig. 1, may 

 be observed, A comparison of this figure with a coloured drawing 

 of true red rot* will show the difference in appearance of the two 

 diseases. Instead of bright red patches and streaks, broken by 

 transversely expanded white areas, there is a diftuse purple or 

 dirty-red colouration, in wdiich brighter red, vertical lines mark 

 the position of the bundles. The tendency of the colour to 

 become muddy at an early period is its most strongly marked 

 character and serves to distinguish the disease from any other 

 known to us. In old cases the red almost disappears, being 

 replaced by an earthy brown. The pith dries up more rapidly 

 than when attacked by Colletotrichuin and becomes hollow. 

 Within the hollow portion, a fiufly grey growth of mould is often 

 found. 



Microscopic examination shows that the stem is infested 

 throughout the reddened portion, which may be confined to a few- 

 joints or extend to the whole length of the cane, by a fungus, 

 whose hyphse ramify through the cells in all directions, penetrat- 

 ing the fibro-vascular bundles as freely as the large-celled paren- 

 chyma of the pith (PI. II, Figs. 2 and 3). Most of the hypha^ 

 are fine, not exceeding 3 ix in diameter in recently infected parts, 

 and either uniform or tapering gradually. They pass from cell to 

 cell through the pits in the walls, when pits are present (Fig. 2), 

 but can also penetrate unbroken walls and seem to have no pre- 

 ference for one tissue more than another. Even when old, they 

 remain hyaline. Occasionally they have been found bearingconidia 

 in the vessels (Fig. 5) and possibly do so also in the parenchj^ma 

 of the pith, as th& condition shown in Fig. 4 appears to repre- 

 sent an early stage of spore-formation. The conidia are small, 

 hyaline, unseptate, oval, and usually appear to be borne singly 

 on short lateral branches of the mycelium. They resemble 

 closely the microconidia frequently found in the vessels of plants 

 affected with the Fusarium wilts. 



* See Mcmoirp, Dept. of Agric. in India, F, No. 3, 1900, PI. I, or Agric. Journ. of India, 11, 

 l'J07, n. XI. 



