1885.] On the transpiration-stream in cut branches. 



351 



Exp. 23. Portugal laurel cut from tree, Aug. 13, 1885. 



Rate 



(i) 



(ii) 



a.m. 



11.29 



43 



Sawed half through*: 



48 



55 



12. 8 



39-0 

 38-8 



36-2 

 36-4 

 36-2 



Sawed half through at right angles to (i), leaving quarter 

 of original transverse section intact : 



p.m. 



12.12 



25 



33-8 

 36-0 



(iii) Sawed so as to leave ^th intact 



p.m. 



12.29 

 43 



Rate 



30-7 

 331 



(iv) Sawed so as to leave T \-th : 



12.47 

 1. 



28-6 

 30-1 



(v) 



Made a tangential cut so as to reduce the bridge of wood 

 through which the current passes to a piece measuring 

 2 mm. tangentially by 1 mm. radially : 



1. 6 

 12 



21-6 

 22-8 



Thus the sectional area of the wood was reduced from 91 

 square mm. to 2 square mm., while the current was only reduced 

 from a velocity of 39 to 22*8, i.e. from 100 to 58 - 5. It is clear 

 therefore that if the leakage of air could depress the rate of ab- 

 sorption, that so deep a section must have produced serious 

 depression. But it will be seen from the rest of the experiment 

 here given that a serious depression only occurred when a small 

 incision 2 mm. in depth was made on the opposite side to the above 

 described deep cut. 



Exp. 23 (continued). 



Time 

 1.12 



Rate 

 22-8 



(vi) Made a cut 16 cm. above and opposite to (v), 

 depth of 2 mm. 



to the 



16 

 19 



20-9 

 22-8 



* At 14 cm. from the cut end of the brauch. 

 diameter. Saw (i) was 7 mm. deep. 



The branch was 13 5 mm. in 



