352 



Mr F. Darwin and Afr R. W. Phillips, [Nov. 23, 



(vii) Out 2 mm. deep, 8 cm. above and opposite to (v) : 



22 



27 



19-8 

 21-2 



(viii) Cut 2 mm. deep, 4 cm. above and opposite to (v) : 



30 | 14-3 

 (ix) Out 2 mm. deep, 1 cm. above and opposite to (v) : 



35 | 7-9 



Thus the large incision described in the first part of Exp. 23 

 only reduced the rate from 39 to 22 - 8, while by sawing to the 

 depth of 2 mm. at several places on the opposite side the rate of 

 absorption was reduced from 22'8 to 7'9\ 



Finally it may be pointed out that by a simple experiment 

 it can be shown that the leakage in question does not take place 

 even in such vascular plants as the Jerusalem artichoke (Helianthus 

 tuber osus). 



Exp. 24. A Portugal laurel was placed in the potometer and 

 gave the readings : 



Time 



4.44 

 52 



Rate 



49-0 

 49-3 



The india-rubber cork (e, fig. 1) was removed and a piece of 

 Helianthus stem, cut square at both ends*, fixed with india-rubber 

 tubing so as to act as a cork. If it were to act as a leaking cork 

 the rate ought to fall. But the following readings show practically 

 no fall : 



Time Rate 



5.5 

 24 



51-8 

 40-3 



The india-rubber cork was then replaced with the result : 



Time 



5.35 



43 



Rate 



40-0 



38-0 



The laurel was then removed and the piece of Helianthus fixed 

 in the potometer, not as a cork but as the transpiring plant, to 

 ascertain what rate of absorption could be produced by the evapo- 

 ration of its free cut end : 



Time 

 5.59 



Rate 

 1-4 



At first 26 cm. in length then after a few minutes reduced to 13-5 cm. 



