252 



Transactions of the Canadian Institute. 



[Vol. VII. 



In order to supplement the experiments to demonstrate the 

 capability of leaves to absorb water, an apparatus was arranged some- 

 what after the method of Bonnet (Fig. 

 3). Leaves with petioles of considerable 

 length were selected and placed with 

 the petioles in the form of a "U"' 

 dipping into a vessel of water. The 

 blades and the cut ends were exposed 

 to the air. Leaves placed under these 

 conditions remained green and turgid 

 much longer than leaves exposed wholly 

 to the air. Several kinds of controls 

 were arranged to support this experi- 

 ment. This indicates that leaves can 

 absorb water through the surface of the 

 FIG. 3. petiole. 



Leaf with petiole immersed in water. a • 1 1 ^ • 1 



A point brought out, durmg the 

 course of these experiments, was that leaves, e.£: Primula, possessing 

 trichomes, seemed to absorb through the petiole more to the advantage 

 of the leaf than did those without trichomes. 



In order to enquire into the matter more fully, an apparatus was 

 arranged as shown in Fig. 4, where the capability of a leaf to absorb 

 water in one surface and transmit it to the other is tested. Leaves of 



FIG. 4. 

 Apparatus for testing the power of absorption and transpiration of leaves. C, a tank containing water 

 or a solution. W W, a piece of plate glass ground to fit the edge of the tank C. O, an aluminum gauze. 

 L, a leaf. CI, a clamp. D, ajar from which the tank can be supplied from time to time. EF, represents 

 the height of liquid due to capillarity. AB represents the amount of pressure up against the leaf L. The 

 margin of the jar is first smeared with grafting wax. As the water evaporates through O the liquid flows 

 towards the left from B, and can be measured readily. When it has reached A' open the clamp on the tube 

 at D and suck the end B until the water comes to the desired point, then close the clamps at B and D ; then 

 open clamp at B. BA may be made long or short to increase or decrease the pressure as may be required. 



