234 K. J. BUTLER. 



fresh, moist and softer sheaths are often exposed. In diseased trees 

 this is just the position in which felted masses of the mycehum of 

 the parasite are found. Fragments of the outer sheaths containing 

 living mycelium no doubt often break of? and remain on the person 

 of the climber. The mycelium itself would readily adhere to his 

 knife. It is easy to see that in repeating the operation in a healthy 

 tree there is every chance of his successfully, if unconsciously, in- 

 oculating it with the parasite. There are indications in some places 

 that the disease has followed lines of communication used by the 

 people, particularly the ferries across the canals which intersect 

 the district. These are no doubt used by the tappers and the 

 matter would be explained if the infection is conveyed by them. 

 In this district the coconut trees are not tapped for toddy and 

 their leaves are rarely cut. Hence they are seldom climbed. Are- 

 canuts are neither tapped nor are their leaves cut and when climbed 

 it is only to remove the bunches of nuts, which project well away 

 from the stem. It is possible that this explains in part the com- 

 parative immunity of these two species of palm. 



The part played by insects in disseminating disease is now 

 well known. Most of the cases recorded are in man or animals, 

 malaria, tick fever, sleeping sickness and surra being instances. 

 Flies are known to be important disease-carriers. A bacterial dis- 

 ease of potatoes is spread, according to Dr. E. F. Smith of the 

 United States Department of Agriculture, a distinguished authority, 

 by insects which convey the bacillus from plant to plant. In the 

 present disease the parasite, being much bulkier than those con- 

 cerned in the above cases, could only be carried by large insects. 

 It so happens that palms are infested by several quite big enough 

 to serve the purpose. The best known are the rhinoceros beetle 

 and the palm weevil, the former of which is very comanon in the 

 district. I have also seen as many as ten scorpions in the crown 

 of a diseased Palmyra. Numbers of birds also frequent the tops 

 of palms. The felted webs of mycelium which are sometimes found 

 on the older sheaths may quite conceivably adhere to the feet of 

 these and be carried from tree to tree. The beetles penetrate into 



