THE LEAVES 83 



second tumbler over the blade. Examine a few 

 hours later. The vapor thrown off by the leaf will 

 have collected in the form of small drops on the 

 inside of the second tumbler. 



103. Measurement of the amount of water thrown 

 off by a plant. Lay a piece of oiled cloth 18 inches 

 square on the table, and in the centre set a potted 

 geranium or tomato. Bring the edges of the cloth 

 up around the pot and tie closely around the base of 

 the stem. Water can now evaporate from the plant 

 only. Set on one pan of a grocer's scale and place 

 weights in the other pan until it balances. 



If a scale is not to be had, suspend a wooden rod 

 by the middle and to each end tie a small bucket. 

 Place the plant in one and weights in the other. 

 Examine a few hours later. The plant will have 

 grown lighter. Remove weights from the opposite 

 end of the beam until the balance is restored. How 

 much weight has been taken out? This represents 

 the amount of the water thrown off by the plant. 



104. Sunlight increases transpiration. Repeat 

 this experiment in the sunlight and compare the 

 amount of water lost with that of the previous 

 experience. 



