THE FLO WEEING PLANT LEAVES 36T 



PHYSIOLOGY 



A. — Transpiration. 



a. Provide two large tumblers, a piece of cardboard 

 large enough to cover the mouth of each, and a 

 large leaf of primrose or Geranium or other suit- 

 able plant. Fill the first tumbler nearly full of 

 water. In the card punch a hole, into which the 

 petiole of the leaf will fit snugly, but will not be 

 compressed. Put the card over the first tumbler, 

 insert the petiole until its lower end projects into 

 the water, then set the second tumbler inverted 

 over the leaf and resting on the card. As a con- 

 trol experiment arrange without the leaf two 

 other tumblers, supported by a piece of cardboard 

 in which no hole has been made. Let the exper- 

 iment stand for a few hours, then examine the 

 upper tumbler in each case. Has any moisture 

 condensed on the inside ? Whence does the moist- 

 ure come ? 



h. From a Geranium, Begonia, Fuchsia, sunflower, or 

 maple, cut a large, weU-developed leaf, seal up the 

 cut end of the petiole with vaseline, lay the leaf 

 in one pan of a delicate balance, weigh the leaf 

 accurately, and make a note of the weight. Let 

 the leaf remain on the balance. How long before 

 the pans change position ? At the end of half an 

 hour balance the leaf again. How much weight 

 has it lost ? Weigh the leaf again at the expira- 

 tion of twenty -four hours. What is the loss? 

 Has the leaf shrunken in size ? What percentage 

 of its weight has been lost by the evaporation of 

 water from its tissues ? Compare the weight of 



