245 



really therefore the same as the one which causes the 

 dying back of branches. 



Infections of cacoa fruits were carried out in tlio labo- 

 ratory and aiso in the field. The pods which were infected 

 in the laboratory were first treated with a 0.5% solution 

 of corrosive subhmate and were then washed with stérile 

 water. The infections material, which was again derived 

 from pods, branches or pure cultures, was introduced 

 into small wounds, made in the fruit by a eut or a 

 puncture. Thèse infections were carried out in large 

 numbers and were uniformly successful, no matter whether 

 the fruits were kept in a moist atmosphère or were laid 

 down or hung up dry. If the treatment with corrossive 

 subllmate was omitted, the infection took place equally 

 well, but in addition ail sorts of other fungi developed, 

 the conidia of which had been présent on the fruit. The 

 pods were however, not attacked if the infection material 

 was placed on the intact frui^" or if such a pod was hung 

 in contact with a diseased one. 



In no single instance did we succeed in infecting pods 

 wiiile they were still hanging on the trees, no matter 

 whether younger or older fruits were taken for this 

 purpose or wiiether an attempt was made in some way 

 or other to keep the place of infection moist. 



If none of the infections of fruits had been successful, 

 it would nevertheless hâve been unjustifiable to draw the 

 conclusion, that Diplodia does not attack pods; since, 

 however, ail fruits eut off from the tree were attacked, 

 but none of those which were still on the tree, the sup- 

 position seems permissible, that perfectly healthy pods are 

 scarcely susceptible to the disease, but that fruits in 

 abnormal conditions are susceptible, like the eut fruits 

 in the experiments. It is very probable therefore, that 

 Diplodia occurs in Surinam in most cases as a saprophyte 



