SUGAR-CANE 89 



sacchari, van Breda) (Fig. 40). This, like many other 

 leaf-spot diseases of plants, causes its greatest injury 

 by reducing the leaf and thus weakening the vitality 

 of the plants, but does not kill. The spots are more 

 or less oval, and 3 to 5 mm. wide when measured 

 across the leaf, and 5 to 15 mm. when measured in the 

 opposite direction. The tissue of the spot is dead, 

 grayish, and surrounded by a narrow brown or reddish 

 ring. When fully matured, minute black points appear. 

 These are the fruiting bodies (perithecia) which are 

 buried in the leaf and project slightly above the surface. 

 They are almost spherical and about 140 mm. in 

 diameter. They contain long, slender, clavate-cylindrical 

 sacs (asci), which contain the spores. The disease occurs 

 in India, Singapore, Java, Borneo, and the West Indies. 



Leaf-splitting Diseases. These diseases are due to one 

 or more species of the genus Mycosphaerella, and are 

 known in the Hawaiian and Fiji Islands where they cause 

 considerable loss. The first appearance of the disease 

 is in the discolorations near the tips of the outer leaves. 

 In a short time light-coloured stripes appear between 

 the fibro-vascular bundles. At first they are narrower 

 than the green stripes, but gradually become wider. 

 In time the leaves become dry and whitish, and begin 

 to split. A careful examination at this time will show 

 small semi-spherical black bodies embedded just below 

 the surface of the leaf. A more careful examination 

 with the microscope shows these bodies to be filled 

 with the spores of the fungus, which are discharged 

 through a small opening, and serve to infect other 

 plants. The disease is very conspicuous and very 

 destructive. The affected shoots should be cut and 

 burned before the spores are ripe. 



Leaf - Spot. - - The brown leaf - spot ( Cercospora 

 longipes, Butler) attacks the young leaves causing 

 narrow oval spots, about ^ inch in diameter, which are 

 clearly visible on both surfaces by the reddish colour. 

 As they grow older they increase in size, are brown in 

 the centre, surrounded by red and a yellow zone. The 



