210 Scientific Proceedings, Royal Dublin Society. 



C and D, was killed with hot water as in the previous experiment, while 

 the leaves on all the branches were protected from injury. The heated region 

 is shown dark in the figure. 



Three days later blotchy discolourations appeared on the lower leaves of 

 B, and less markedly on some of those of A, B, and C. 



On the fourteenth day the four lowermost leaves of D were completely 

 discoloured, and a small blotch had appeared on the fifth leaf from the base, 

 while the seven leaves above were quite healthy. On A there were five 

 leaves dead ; on B two small ones and two large leaves blotched ; on C there 

 was one withered and crisp and one blotched. 



At this stage 14 ems. at the base of C were heated, the leaves above being 

 protected. 



On the next day all the leaves of C were stained and beginning to curl. 

 No further changes were noticed on A and B. 



Six days after the heating of C all its leaves were dead, while still the 

 uppermost leaf of D was unaffected, although its supply had now been 

 drawn for twenty days through a piece of dead stem, 22 cms. in length. 



The results of this experiment drive us to the conclusion that deleterious 

 substances were washed from the stem below D and transferred into the lateral 

 branches A, B, and C ; for the changes in the leaves of D were no more 

 noticeable than those in the leaves of the other branches, into which evidently 

 the major part of the poisonous substances had been distributed. The 

 ohanges observed in the leaves of C after it had been heated indicate the 

 extent and rapidity of the injuries we miglit have expected in D had the 

 heated region below its base not been washed out. 



Both experiments seem to afford conclusive evidence that, with the 

 killing of the cells of the stem by heat, changes are introduced into the 

 sap which are largely responsible for the alterations in the leaves above. 

 Hence the morbid changes there cannot validly be attributed to the cutting-ofi 

 of the supply, but rather should be assigned to its contamination. 



