56 Plants and their Ways in Soiith Africa 



and set aside for another day. What has happened? The 

 thick syrup has drawn the water out. The " cell sap " has 

 passed in the direction of the stronger solution. Try the 

 same experiment with salt instead of sugar. 



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 ? 



Boil a piece of beet-root or a green bean pod for a few 

 minutes in water. When removed they are quite 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 coloured sap. Living 

 cells can retain the sap until a certain amount of pressure is 

 set up within the cell. This keeps the plant firm. Then they 

 give it up to cells with denser contents. 



Protoplasm acts because it is alive. Roots not olny 

 draw material from the soil, but they send out an acid to 

 dissolve the hard rocks. 



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. 



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 

 acid gas, as we shall find out they do. 



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 the cut 

 end and run down the stem. Pressure from below forces it up. 

 In order to see how long this continues, we may try another 

 experiment. It will require a vigorous young plant such as a 



