DISEASES OF COCONUT 179 



or red mingled with mustard yellow. A vertical section shows 

 the zone completely surrounding the base of the stem, extending 

 upwards as a solid band of reddened tissue to about half its 

 height, then breaking up into longitudinal streaks and finally 

 into scattered dots about i mm. in diameter. In the latter form 

 it extends to the soft meristem underlying the bud, in which 

 region the dots appear generally dispersed below the flattened 

 apex of the stem. In very exceptional cases the discoloration 

 in the stem as a whole is central. 



When the leaves of a tree in this stage are split open in the 

 median line a similar red-spotted or red and yellow streaked 

 discoloration is revealed in the leaf-stalk, extending in the fully 

 developed leaves from near the base to a distance of from 6 

 inches to 2^ feet outwards. In the older leaves it becomes 

 masked by the development of brown rot or by the natural 

 browning of the tissues. In the leaves of the central column 

 which still remain green, the internal discoloration of the petiole 

 appears with great intensity, and often extends to the unde- 

 veloped leaves which they enclose. 



In the oldest leaves the infestation extends to the base, 

 but has no apparent connection with the red zone in the stem. 

 As the successive leaves are examined in order of age the dis- 

 coloration recedes upwards, but has been frequently seen to 

 retain at first a narrow connection with the base on the dorsal 

 side. In the soft white central leaves the petiole for a distance 

 of from several inches to a foot from the base is usually normal 

 in appearance, and then often contains an enclosed central 

 infestation marked by vivid red and yellow spots and sometimes 

 extending for two or three feet within the rachis. 



In the roots the visible effect of the disease is confined to 

 the cortex, which consists of radial lamellae loosely packed into 

 the region between the horny hypoderm and the central woody 

 strand. This tissue is pure white and soft when healthy, but 

 when infested it becomes dry and flaky, and is discoloured, 

 first light yellow or pink, then dark yellow or reddish brown. 

 The infestation may extend for any distance from an inch or 

 two to 10 or 12 feet from the point of attachment ; it is con- 

 tinuous, and decreases in intensity in the outward direction. 

 Infested trees vary very widely in the extent to which the roots 

 are affected. A tree which is fully infested in stem and leaves 

 may show only the very beginnings of infestation in the roots. 



Causation. 



While fungi and bacteria are rare and casual in their occur- 

 rence in the infested tissues until an advanced stage is reached 

 and decay begins, there is a perfectly constant association of 

 the worm with the lesions existing in the stem, leaves and roots ; 

 an association which begins with the first trace of discoloration 

 and persists until the infested tissue is dead and decayed. The 



