The diseases and pests of the rubber tree . a short oblique wound, caused bylightmng, in process of healing, and the accompanyingdiagram (Fig. 34) was drawn fromthe cross-section of it. The woodis indicated in the diagram byradial lines, and the cortex bythe dotted areas. The project-ing edges of the original cortexhave died back, and a growth ofcallus has taken place over theedges of the wound from theoriginal cambium. In addition,there is new growth (indicatedby dose lines) on either side ofthe wound in the split along thelast annual ring. The blackregions in the latter situationindicate dea
The diseases and pests of the rubber tree . a short oblique wound, caused bylightmng, in process of healing, and the accompanyingdiagram (Fig. 34) was drawn fromthe cross-section of it. The woodis indicated in the diagram byradial lines, and the cortex bythe dotted areas. The project-ing edges of the original cortexhave died back, and a growth ofcallus has taken place over theedges of the wound from theoriginal cambium. In addition,there is new growth (indicatedby dose lines) on either side ofthe wound in the split along thelast annual ring. The blackregions in the latter situationindicate dead tissue. The illustrations describeddepict a well-defined case. Butmany instances occur in whichthe sear is small, and no openwound is evident. In these casesthe outer bark is often notcracked, and nothing is observeduntil it scales off and reveals thehealed scar. Such occurrencesare fairly common in one dis-trict in Ceylon, especially ontwo estates on opposite sides of the same valley. The latter case is illustrated in Fig. 35. The stem,. Fig. 35.—Lightning scars, x J. 204 THE RUBBER TREE c=ap. wMcli in the specimen photographed was five inches indiameter, is covered with circular or oval scars one ortwo inches in diameter. These scars occur scattered overthe surface of the trees in large nxmibers. A small patch ofbark, often longitudinally cracked, scales ofi, displaying theunderlying scar, surrounded by normal bark which is usuallyslightly upturned round the edge. Sometimes exuded latexis present on the outer bark scale. The surface of the scartissue is blackish, generally radially grooved and some-times depressed in the centre. When the scars are largethe stem is usually swollen, so that old examples are raised,as though a nodule had developed ia the underlyingcortex. On stripping ofE the cortex over an affected patch, themain wood of the stem is found to be raised in a graduallyelevated swelling under each scar. In some instances thesurface of the wood is irregular, wit
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