117 



of cases natural infection actually does take place by germinating 

 spores without any previous wounding of the rind. I have no doubt 

 that, had time permitted, further experiments would have conclusively 

 proved that this is the case. 



Natural Infection. — We should exp act that since moisture is essen- 

 tial for the germination of spores that infection of cacao pods would 

 take place naturally at those points where water is likely to remain 

 for the longest time. These points are the groove rouud the insertion 

 of the pod stalk, the points where a pod comes in contact with a branch, 

 and ;the free end of the pod itself where after rain a drop of water re- 

 mains for some time after the rest of the surface is quite dry. Obser- 

 vation shows that the disease generally starts from these points. 

 Since infection takes place by means of spores, we should also expect 

 the disease to be most prevalent, where these spores are present in 

 greatest numbers. Undoubtedly this is near the "breaking-grounds" 

 since here it was noted that the fungus unler discussion lives on the 

 old husks of the cacao pods on which it forms myriads of spores. 

 These can be seen with the naked eye as a black dust covering the 

 blackened pods. It is actually found that the disease occurs to a 

 greater extent here than elsewhere. The same fungus is also to be 

 found on the dead prunings which are sometimes left under the cacao 

 trees and also on diseased sugar cane in places where this cultivation 

 is carried on among the young cacao 



General Conclusions. — There is no doubt that the "brown rot" of 

 the cacao pods is due to a fungus, and not as is supposed in some parts 

 of Grenada to " Thrips," sunburn or to over- ripeness Infection takes 

 place by means of spores which may set up the disease at a wounded 

 surface or very probably at those points where water is apt to remain 

 longest without any bruising of the rind. The fungus is wilely dis- 

 tributed in the island occurring on the old husks of the cacao pod, on 

 old prunings, and even on diseas d sugar cane. 



Damage done to Cacao Trees by the "Brown Rot" Fungus. 

 During the progress of the investigation it appeared highly probable 

 that some damage was being done by this fungus to the cacao trees 

 themselves and especially to the young cultivation. It was found that 

 young cacao trees from two to six years old and even more, were dying 

 off from some reason that was not at once apparent. " Thrips" were 

 usually alleged to be the cause, but I saw no reason to accept this view 

 as the number of these insects present was not sufficient to cause any 

 damage whatsoever. On examination of the trees in question I found 

 they were being attacked by a fungus which was apparently identical 

 with that causing the brown-rot of the pods. Unfortunately there is 

 no striking external evidence of the presence ol this fungus in the 

 diseased trees The branches die off and decay spreads to the stem 

 after which death rapidlv takes place. The dead wood turns brown 

 and dries up while there is a gradual transition between the dead and 

 still living portions of the branch or tree. In tnese regions the brown- 

 ish discolouration is seen to be due to a fungus which can be traced in 

 the wood to some distance in front of the discoloured areas. Under 

 the cracks of the recently killed bark the spore sacs of the fungus are 

 formed and the dark masses of ejected spores can sometimes be made 



