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out by careful examination with a lens or magnifying glass. It now 

 became necessary to prove whether or not the " brown-rot" fungus is 

 really the cause of the damage done to the cacao trees in question, and 

 in order to do this, infection experiments were made on healthy cacao 

 trees at the Botanic Station. 



Infection Experiments. — Experiments were carried out on young 

 cacao plants growing in bamboo pots, on trees eighteen months old and 

 on adult trees. 



1. On February 24tb, two branches about two inches in diameter of 

 a healthy tree were selected for the experiment. The outer dry bark 

 was carefully peeled off about one square inch of the surface which was 

 then sterilised to kill any fungus spores upon it. A small chamber 

 was then made with a sterile knife at these points by raising the bark 

 and cutting out the tissues underneath down to the wood. Into one 

 of these a portion of a pure cultivation of the brown-rot fungus of the 

 pod was introduced and the whole covered with a water tight bandage. 

 The second branch was treated in exactly the same way except that no 

 fungus was introduced. This served as a check experiment. The re- 

 sult was surprising. On March 4th — eight days afterwards — it was 

 found (in the case of the branch where fungus had been introduced) 

 that the bark had been killed to a distance of eight inches above and be- 

 low the point of infection and the branch was nearly " ringed." The at- 

 tacked bark wasfoundto be filled with the "roots" of a fungus which had 

 also made their way into the young wood to the depth of a quarter of 

 an inch under the point of infeetion and to about a foot above and 

 below the chamber where the fungus was introduced. Spore sacs con- 

 taining spores were formed under the bark and these agreed in all their 

 characters with those found on the brown pods. The control or check 

 experiment showed no infection. 



2. Eight healthy cacao plants, about eight months old, growing in 

 bamboo pots were next experimented upon. On March 4th, Nos. 1 

 and 2 were inoculated with the spores of the fungus taken from a pod 

 attacked by "brown-rot" by introducing them into a slit made in the 

 bark of the stem. Nos. 3 and 4 were similarly inoculated with small 

 portions of the diseased rind of a cacao pod attacked by "brown-rot" 

 which contained the active " roots" of the fungus. Nos. 5 and 6 were 

 inoculated with "brown rot" fungus growing artificially in a pure cul- 

 tivation, and Nos. 7 and 8 were control plants. After inoculation, the 

 plants were placed in the shade and watered daily. On March 12th 

 the disease had established itself to a greater or less extent in all the 

 plants from one to six while Kos. 1 and 6 themselves had been killed 

 by the disease. The control plants showed no infection. 



3. Four extremely vigorous young cacao trees about eighteen months 

 old which had been planted out at the usual time were selected for this 

 experiment. On March 4th, three were infected under the bark with 

 fungus spores, diseased rind from a cacao pod attacked by " brown rot" 

 and artificially grown fungus respectively. The fourth tree was treated 

 exactly like the rest except that no fungus or spores were introduced 

 and served as a check experiment. On March 12th the disease had 

 setablished itself in the first three trees and especially in No. 2 which 

 had been inoculated with a small portion of the tissue of a diseased 

 pod. Here the disease could be traced in the young tree to about eight 



