82 



LABORATORY MANUAL 



cardboard. Fill one tumbler with water and place 

 the cardboard over it, with the cut end of the geranium 

 extending into the water. Paraffin the 

 entire upper surface of the cardboard 

 to prevent any evaporation of water 

 through it or around the stem of the 

 geranium. Over the leaves of the 

 geranium invert the second tumbler 

 and set the experiment aside for a few 

 hours. Then examine the inside of the 

 upper tumbler. How do you account 

 for the condition found ? 



Fig. 29. 



Exercise 53. Rate of Transpiration. 

 Object: To determine the difference in the rates of 

 loss of water in different plants. 



Cobalt paper 

 Rubber plant 

 Nasturtium 



Apparatus 



Scissors 

 Paper clips 



Directions: Cobalt paper is prepared by saturating 

 filter paper in a solution of cobalt chloride. The paper 

 is then thoroughly dried in an oven. What is the color 

 of the paper? On a small piece of paper place a drop 

 of water. What happens ? Cut several pieces of paper, 

 each about one inch square. With a clip fasten one 

 piece on the upper, and another piece on the under 

 surface of a leaf of a rubber plant. Note the exact 

 time that this is done. Watch the paper. What change 

 do you observe? How long did it take to produce this 



