426 DISEASES OF CULTIVATED PLANTS 



running into each other, and forming large brownish patches 

 on living leaves of the horse-chestnut. Spores rod-like, 

 curved, septate, 55-60X3 /*. 



Septoria graminis (Desm.) has very minute perithecia 

 which are densely crowded, forming long, greyish, nebulous 

 patches on the leaves of cereals. The conidia are about the 

 same length as those of Septoria tritici (Desm.), but con- 

 siderably narrower and slightly thickened at one end ; septa 

 not obvious. 



DIPLODIA (FRIES.) 



Perithecia subcarbonaceous, black, typically papillate ; 

 conidia elliptical, i -septate, coloured. 



Brown rot of cacao pods (Diplodia cacaoicola, P. Henn.) 

 is responsible for a considerable amount of injury to cacao 

 pods in the West Indies. It has also occurred in Africa. 

 When a pod is infected a circular brown patch makes its 

 appearance, which gradually extends all over the pod, and 

 causes complete destruction of the rind and its contents. 

 The time taken in the destruction of a pod varies according 

 to its state of ripeness, but is usually included between six 

 and ten days from the period of infection. The disease 

 usually commences at the point of insertion of the stalk or 

 at the free end of the pod, but may occur at other points, 

 especially if the rind has been injured, or where it comes in 

 contact with a branch. Diseased pods are especially 

 numerous in the vicinity of the ' breaking grounds,' where the 

 beans are extracted by the pickers. The disease soon 

 spreads to the 'beans,' which are speedily destroyed by a 

 greyish mycelium. When the diseased patches on the rind 

 are about an inch in diameter, the small black perithecia 

 commence to appear at the centre of the patch, and soon 

 liberate their brown i-septate conidia, averaging 20 x 10 p. 



There is no cure nor means of checking the disease when 

 a pod is once infected. It is suggested that pods should not 

 be allowed to get too ripe, as they are most liable to infection 

 at this stage. All husks, shells, etc., should be destroyed, as 

 should also dead cacao-trees and prunings, on which the 

 fungus also occurs. 



Howard, West Indian Bull., 2, p. 192 (1901). 

 Massee, Kew Bull. 



