Some Simple Physiological Demonstrations. 193 
4. Rate of flow of water through the wood .—For the purpose 
of this experiment, as for others ordinarily requiring the use of an 
air-pump, the same method as described in the two previous cases 
can be employed. By a simple modification it can be adapted for 
comparative results. Thus, if the flask in Fig. 1, A, be fitted with 
a two-holed stopper, each hole bearing a piece of glass tubing like 
that shown in the figure, the rate of flow through two branches 
(e.g., those of a Dicotyledon and a Conifer), subjected to identical 
amounts of negative pressure, can be compared. The upper cut 
E.TS 
Fig. 1. For description see Text. 
