The soil and the plant 



73 



Before we can account for this observation, we must 

 ascertain a little more closely what becomes of the 

 water the plant takes up. It certainly does not all stay 

 in the plant, and the only way out seems to be through 

 the leaves. Put a test tube on the leaf of a growing 

 plant and fix a split cork round the stem : leave in sun- 



Fig. 34 h. 

 Plants collected on moist loam. All have wide leaves 



light for a few hours and notice that water begins to 

 collect in the test tube (Fig. 35). The experiment 

 shows that water passes out of the plant through the 

 leaves. 



This experiment was first made by Stephen Hales, 

 and described by him thus in 1727: " Having by many 



