262 E. J. BUTLER. 



penetrated was tliree and-a-half in eleven days ; in the second, 5 

 were penetrated in 15 days. Both these were done in the period of 

 heavy monsoon rains. In the third, carried out in late September 

 in bright sunny weather at the end of the soutli-west monsoon, 

 there were only 3, 4 and 6 sheaths respectively, penetrated in 28 days 

 in the three trees inoculated. In the 4th, which extended from Nov- 

 ember 10th to December 10th, the progress was still slower. The 

 experiment quoted on page 238 showed that in two trees 10 and 12 

 sheaths had been penetrated in the period from March 24th to 

 September 10th, which includes the driest and wettest months of the 

 year. Hence it would appear that the progress of infection may 

 be rapid in the rains but gets slower as the amount of rain 

 diminishes and the temperature falls in the cold weather. It is 

 probable that in the last quoted experiment, most of the exten- 

 sion took place subsequent to the onset of the monsoon in June, 

 as there is a great deal of observational evidence to show that little 

 occurs ordinarily in March, April and May. 



IX. —Dormant condition of the Parasite. 



The difference in the rate of progress of the disease in inoculated 

 trees leads us directly to the consideration of cases which suggest 

 that the parasite may pass into a dormant condition for a greater 

 or less period and resume growth again. It was frequently observed 

 during the earlier period of the campaign undertaken to destroy 

 all diseased trees in the affected area, that fresh deaths continued 

 to recur after a locality had been cleared of dead and dying palms. 

 At first these were believed to be new infections conveyed in some 

 manner unknown. Then it was noticed that there was a difference 

 in the distribution of these cases as compared with outbreaks which 

 were undoubtedly due to fresh infections, as when a village became 

 attacked for the first time. In the latter case the deaths were in 

 groups or often in one small part of a village only, indicating spread 

 from one or a few early attacked trees. The deaths in villages 

 that had been one or more times cleared of all outwardly diseased 

 trees occurred scattered throughout the cleared area. In Amalapur 



