in ASCENT OF SAP IN STEMS 75 



water transmitted per 10 min., and the abscissse are the 

 times in hours. The full line connects the successive 

 observations on the control branch ; the dotted line joins 

 the observations on the experimental branch. The gap 

 indicates the interval during which the cistern was emptied, 

 and the steam was applied to the experimental branch. 



Change taking place in the experimental branch, demon- 

 strated by the exit of coloured liquid below after the 

 application of the high temperature, renders the experi- 

 ment somewhat unsatisfactory ; for, although the experi- 

 ment gives no indication that the removal of vital processes 

 from the stem does away with lifting forces opposing the 

 downward motion of water, yet it is just conceivable that, 

 if these forces previously existed and were removed, the 

 clogging of the branch during the steaming might just 

 compensate for their removal. The possibility of such a 

 coincidence, though very improbable, suggested the use of 

 picric acid as a killing agent in place of steam. 



The experiment was at first arranged in exactly the 

 same manner as before ; and the initial rates of trans- 

 mission of the experimental and control branches were 

 determined. Then some dry picric acid was introduced 

 into the water-tube of the experimental branch, and the 

 observations were continued. No change, which could be 

 assigned to the removal of vital actions by the picric acid, 

 could be detected in the rates of transmission, even when 

 the acid appeared at the lower end of the experimental 

 branch. 



The gradual killing of the branch and the slow penetration 

 of the picric acid in this method are open to objection, and 

 would tend to render a change due to death less noticeable. 

 To remove this objection, a modification was introduced 

 by means of which the picric acid is quickly forced through 

 the stem under pressure ; and, in order to place the control 

 under similar conditions, distilled water is simultaneously 

 forced through it. This is arranged by having the tubes 



