THE LEAF. 65 



II. Cut off a strong, well-developed leaf of a primrose, 

 immerse the blade of the leaf in water, and placing the 

 cut end of the petiole in the mouth, inhale forcibly. Do 

 you obtain any proof that the inside of the leaf is in com- 

 munication with the atmosphere ? 



III. Take any leafy plant of convenient size that is 

 growing in a flower pot, cover the pot with a piece of 

 dentists' rubber, bringing it up around the stem of the 

 plant and tying it so that no water can be given off 

 except through the plant itself. Weigh the whole, and at 

 the end of twenty-four hours weigh again. To what is the 

 loss of weight due ? 



IV. Vary the last experiment by employing different 

 kinds of plants, as, for example, some with leathery and 

 others with soft leaves ; also by placing some in the sun- 

 light and others in the shade, in the open air and in a 

 closed room. What are some of the conditions affecting 

 transpiration ? 



Respiration. 



Respiration is a function of every living cell. Hence 

 leaves are to be thought of as organs of respiration in so 

 far as they expose a very large number of active cells to 

 the atmosphere, although they do not really " correspond 

 to the lungs of animals." We may therefore employ 

 leaves to demonstrate the process of respiration, or we 

 may use flowers or germinating seeds. 



Take three wide-mouthed bottles and fill each two-thirds 

 full, the first of fresh leaves, the second of germinating 

 peas, and the third of flowers. Cork and allow to stand a 

 few hours. Test the air in the bottles at the beginning 

 and close of the experiment by introducing a homoeopathic 

 vial containing limewater, also by inserting a lighted 

 match. What is the result? 



