240 



EXPERIMENTS WITH PLANTS 



HI. Modification 

 of arrangement 

 shown in Fig. 

 140. 



Trim away from the Pine branch all its 

 leaves and twigs (the wounds made in so 

 doing should be covered with sealing- 

 wax), insert the base of the branch air- 

 tight in the cork, fill the large tube brimful 

 of water and insert the cork with its 

 branch so as to exclude air as much as 

 possible. Pass a wire over both corks, as 

 shown in the figure, and secure it firmly. 

 Attach a glass tube five or six inches long 

 to the top of the branch, and pour mer- 

 cury into the long tube until there is suffi- 

 cient pressure to make water flow through 

 the branch at the same rate as it flowed 

 when intact (as shown by the weighing) . 

 Perform the same experiment with the 

 Oak branch. 1 



The same experiment may be per- 

 formed by basing the comparison on the 

 rapidity of rise of the sap as shown by eosin 

 solution (instead of on the amount) . In this 

 case two similar branches from the same 

 tree should be compared, one being placed 

 intact in eosin solution, the other stripped 

 and connected with the tube as before, so 

 as to force the eosin solution through it. 



1 It is possible to perform the experiment on short twigs by pouring water 

 instead of mercury into the long tube. 



