60 Plants and their Ways in South Africa 



This pretty experiment should not be omitted. Cobalt chloride may 

 be obtained from the chemist. Sixpennyworth will prepare sufficient 

 paper to last some time. It will keep, and the same piece may be used 

 repeatedly. 



Ex. 23. Place under the bell-jar fruits of Erodium or Pelargonium and 

 watch them uncoil ; remove, dry in the sun, and repeat the experiment. 



Ex. 24. Place a leafy shoot in a glass U-tube (a straight piece of 

 glass may be heated and bent the required shape). Connect the shoot to 

 the tube with rubber tubing so that no air can enter. The tube should be 

 filled from the other end with water. When the water has been nearly 

 drawn out of one arm, pour in mercury. The mercury, which is very 

 heavy, will be raised higher in the arm of the tube containing the plant 

 than in the other, so the leaves can do some heavy lifting. 



Does water pass from leaves in any form but 

 vapour ? If so, it must be in drops. Place a pot of germin- 

 ating Indian Corn or Oats under a bell-jar overnight. The 

 next morning notice the tip of each blade where there are 

 small holes through which water can pass in drops. 



After a warm night or in shaded places the tips of the 

 young blades in a corn field may be seen beautifully aglisten 

 with drops. 



They are not dewdrops, for they are there when no dew is 

 formed on other plants. Other plants show the same nicely. 

 See the drops on Tropceolum (Nasturtium) plants where open- 

 ings on the leaves are placed at the end of each strong vein. 



On a very warm afternoon in summer an entire Rose bush 

 may have the serrate points of every leaf glistening with a drop 

 of water. 



Does vapour pass off in equal amount from both 

 leaf surfaces ? 



Ex. 25. Place an Apricot leaf between two sheets of filter paper soaked 

 in cobalt chloride. 1 The leaf should be dried from all surface water ; then 

 place between two plates of glass. 2 On all place a light weight. In half 

 an hour, or less, eximine. The paper next the under side of the leaf will 

 be red, that on the upper surface will be only slightly changed. Moisture 

 given off by the leaf has changed the colour. 



1 Try the same experiment with a Sunflower leaf; with a leaf from a 

 pepper tree. 



2 Line two pieces of sheet cork with plush and cut holes in the centre 

 of each. Fasten a cover glass over each hole. This may be fastened 

 over the cobalt chloride paper with a rubber band. 



