58 Plants and their Ways in South Africa 



direction of the stronger solution. Try the same experiment with salt 

 instead of sugar. 



Ex. 14. Dissolve out the lime from the shells of two eggs with dilute 

 hydrochloric acid. Place one in fresh water and the other in a salt solu- 

 tion. If the salt solution is of the right strength, diffusion will take place 

 and the egg will shrink, while the other will take up water by endosmosis 

 and will greatly increase in size. 



Ex. 15. Remove the shell from one end of an egg, taking care not to 

 injure the thin inner membrane ; insert a slender glass tube at the other 

 end, letting it come into contact with the white and seal the join with wax. 

 Place the egg upright in a slender jar which has been nearly filled with 

 water to which a few drops of methyl blue has been added, so that the 

 water comes into contact with the uninjured membrane. In a short time 

 clear water will rise in the tube. 



Ex. 16. Place the leaf stalk of a pumpkin in water which has had 

 salt dissolved in it. Leave for a few hours. How does the stalk look ? 

 Now wash off the salt and place in fresh water. Notice a few hours later. 

 How has the stalk altered ? 



Ex. 17. Boil a piece of beet-root or a green bean pod for a few min- 

 utes in water. When removed they arequite limp. The water is coloured. 

 When placed in fresh water they do not become firm again. Boiling has 

 killed the living protoplasm. The dead membrane cannot hold the col- 

 oured sap. Living cells can retain the sap until a certain amount of pres- 

 sure is set up within the cell. This keeps the plant firm. Protoplasm 

 acts because it is alive. 



Roots not only draw material from the soil, but they send 

 out an acid which dissolves the hard rocks. 



Ex. 18. Germinate seeds in a flower-pot into which has been placed 

 an inclined piece of marble having the smooth side up. Keep the roots 

 watered until the pot is well filled with their growth. Remove the marble, 

 and look on it for the etching made by the roots. 



Ex. 19. Fasten to a glass slide with a rubber band a piece of blue 

 litmus paper, between the glass and a germinating seed. The glass and 

 paper should be previously moistened well with steam or distilled water. 

 Place within a covered dish. As the radicle lengthens, notice the faint 

 change in colour on the paper. Acid colours blue litmus paper red. It 

 may be the carbonic acid which is formed when roots breathe out carbonic 

 v acid gas, as we shall find out they do. Besides carbonic acid, an acid salt 

 is excreted from roots, acid potassium phosphate. 1 



How the Water is Lifted up. Within the "bottle 

 cell," pressure made the membrane bulge. Cut off growing 

 bean stems below the cotyledons. Drops of water collect at 



1 Not all roots excrete sufficient acid to show these tests. 



