118 



most liable to succumb, although many old trees were in a diseased 

 condition. 



KsWhen the [root system, reduced in extent by the action of the 

 fungus, is incapable of supplying the needs of the plant, the 

 leaves commence to roll up, so as to reduce evaporation. Subse- 

 quently the leaves do not obtain sufficient water to keep their 

 tissues alive and then they gradually begin to turn yellow and to 

 dry up, the leaves are, therefore, unable to carry on their functions 

 and the whole mechanism is thrown out of action. The general 

 appearance of the plant is that of one suffering from ' drought.' 



The petioles of the leaves are also filled with fungus mycelium. 

 This may be noticed in all dying leaves, for their petioles are 

 blackish in colour. No instance has been found of the mycelium 

 passing from the petioles into the stems of the trees, and if a section 

 be cut through a terminal bud of a freshly diseased tree, a sharp 

 line of demarcation will be noticed between the diseased petioles 

 and the healthy bud. This mycelium cuts off much food to and 

 from the leaf and therefore assists in the general disorganization 

 of the functions of several parts of the plant. 



The reasons for attributing the damage to fungus in the roots 

 are as follows : — 



(I.) The external ^symptoms of the disease suggest lack of 



water. 

 (2.) The roots of all trees examined were in a diseased con- 

 dition through the presence of a fungus. 

 (3.) Some instances were noticed in which the roots of dead 

 or dying trees were diseased while no fungal mycelium 

 could be detected in the petioles. 

 (4.) As a rule several leaves begin to become wilted and 

 yellow at the same time, whereas if the fungus in the 

 petioles were the primary cause of the trouble, it would 

 be expected that first one leaf and then another, and not 

 a considerable number at once would become attacked 

 and die. 

 (5.) The red rim of discoloration in the stem which generally 

 begins at the base of the tree first and then spreads up- 

 wards is closely associated with the death of the roots 

 and the wilting of the leaves, but it is often noticed in 

 the stem before the leaves turn yellow and before any 

 fungus can be noted in the petioles. It would appear 

 therefore that the discoloration in the stem should be 

 attributed to the stoppage of water supply from below 

 rather than to disorganization produced by cutting off of 

 manufactured food supplies by the leaves. 

 18. The general opinion of the planters of coco-nuts was that 

 this disease is due to the weakness of the plants produced by the 

 setting of immature nuts. In some districts histories of weather 

 beaten cargoes of green nuts been driven on the shores and the 

 nuts used for planting purposes were held out as the cause of the 

 trouble. This disease however is not limited to a few scattered 

 trees, and evidence distinctly points to its being infectious. A 



