246 E. J. BUTLER. 



of these, exposed to the air, are usually brown and dry and are 

 moreover partially hidden by the cut bases of older leaves, and in 

 coconuts by loose fibrous layers. Hence it is not possible to detect 

 the spots on the outer sheaths in standing trees, and as a rule the 

 first indication visible without felling the tree is the withering of the 

 central shoot or of one of the expanded leaves. In the great majority 

 of cases it is the central shoot that withers first. Tliis is undoubtedly 

 because the heart of the bud, which consists of the young unexpanded 

 leaves and their bases, is very soft and full of sap, while the sheaths 

 towards the outside are progressively harder and less juicy. Hence 

 the parasite grows through these from the outside without, as a rule, 

 much lateral exj)ansion, and forms on them only isolated spots or 

 patches, not large enough to cause the leaves above to die from stop- 

 page of food supplies and loss of support. As soon as it reaches 

 the young soft tissues of the unexpanded leaves it spreads with great 

 rapidity and soon destroys the centre of the bud. The cluster of 

 partially expanded leaves in the centre of the crown is next affected, 

 and in this stage the presence of the disease can be detected 

 from below. Less often the first leaf to show morbid changes visible 

 from below is one of those fully expanded. It is merely a ques- 

 tion of accidental circumstances favouring the growth of the 

 parasite in particular places. The affected leaves first turn pale 

 and then wither, becoming dry and yellowish brown in ten or 

 twelve days. 



Besides the leaf-sheaths the parasite also occurs on the leaf- 

 blades in certain cases, and even on the petioles. One of the figures 

 on plate III shows the characters of the attack on the blade. From 

 the symmetrical nature of the spots on the segments of the leaf, 

 as well as from several cases actually observed, it is clear that the 

 attack occurs while the young blade is still folded within the bud. 

 In some of these cases the tissues above the spots die and fall away, 

 and the blade appears as if cut across at the level of the disease. 

 Very few cases of attack on the petiole have been seen. In one an 

 expanded leaf was bent and hanging down from about the centre 

 of the petiole, where a large, soft, brown and sunken spot passed right 



