260 COCOA CHAP. 



Probably this disease will also be found in many other 

 countries where " canker" and " black rot " occur. 



The black rot of pods (Phytophtliora Faberi). 

 This disease is very common, and is probably to be 

 found as a more or less serious pest in every cocoa- 

 growing country. At any rate it has been observed in 

 every country where cocoa diseases have been the object 

 of investigation (the Antilles, Surinam, Kamerun, San 

 Thome, Ceylon, Java, Samoa). 



The fungus may attack pods of any age, but the 

 true parasitic character is particularly clear when large 

 pods are attacked. On such fruits a brownish dis- 

 coloration appears, which may start anywhere on the 

 surface, but generally at the tip or at the stem end. 

 It spreads rapidly over the whole fruit, which finally 

 becomes black, while white powdery masses begin to 

 appear on the surface, especially along the furrows. 1 

 These white masses are the spores of the parasite ; they 

 are spread by the wind to other fruits, on which they 

 germinate, and into which the fungus penetrates, causing 

 again black rot. 



As a rule, the germination of these spores (" conidio- 

 spores ") does not take place in the same way as in the 

 case of most other fungi. If placed in water they 

 germinate by letting out from 10 to 30 small so-called 

 " zoospores," which swim by means of hair-like organs 

 of locomotion, called cilia. They soon lose these cilia 

 and send out a germ tube, like most spores when 

 germinating. Sometimes the conidiospores germinate 

 directly by means of a germinating tube. Simul- 

 taneously with the spore-production on the outside of 

 the attacked fruits, another kind of spore is formed 

 within the tissues of the pod. These are the so-called 

 " oospores " which serve as resting spores, and may 

 retain their vitality for a long time. 



Though the growth of almost every fungus is 

 favoured by moisture and humidity, this is especially 



1 A good description has been given by Rorer (Bulletin of the Dept. of 

 Agriculture, Trinidad, July 1910). 



