xi ABSORPTION AND MOVEMENT OF WATER 141 



which can transpire. The following experiments will show that 

 plants lose water : 



EXPT. 129. Take up three well -developed Mustard plants by their 

 roots and put one in a dry place, such as on a table in a warm room. 

 Place another with its roots in water, and the third in a dark cupboard. 

 Examine at the end of a few hours. Note 



(i) The plant placed on the table is withered. 



(ii) The one in the dark cupboard is in a far better state than 

 the first. 



(iii) The plant in water is unaltered ; the roots have taken water in as 

 fast as it has been transpired. 



(iv) Plants give out water more actively in a light than in a dark 

 place. 



EXPT. 130. Obtain a potted plant, and cover the soil either with 

 tinfoil or cardboard to prevent evaporation from it. Now place the 

 pot and its contents on the pan of a scale and weigh it. Note 

 (i) That the pot and its contents lose weight. 



(ii) This must be due to the leaves and stem giving out moisture. 



(iii) The longer it stays on the scale the lighter it becomes. 



(iv) This experiment can be performed before a class even in winter, 

 using either the electric light or gas. 



EXPT. 131. Cover the soil of a potted plant with tinfoil or card- 

 board as before, and cover the plant with a bell jar, and place the whole 

 arrangement in sunlight. Note 



(i) The inside of the jar is soon covered with moisture. 



(ii) The moisture disappears at night. 



(iii) There is only one source for the moisture, viz., the leaves and 

 stems of the plant. 



(iv) The moisture disappears at night because the plant no longer 

 transpires ; the moisture is condensed and runs down the jar. 



To Prove that a given Green-leaf is losing 

 Moisture. 



EXPT. 132. Place some white blotting paper in a weak solution of 

 cobalt chloride. Dry^the paper either by holding it before a fire or in 

 direct sunlight ; it turns blue. 



Hold a piece of this paper near a leaf which is still on the tree. 

 Note 



(i) That the paper slowly becomes red ; the quicker the colour changes, 

 the more moisture the leaf is giving out. 



(ii) A similar piece of paper should be exposed to the air at the same 

 time as a test of the atmospheric condition with regard to moisture. 



EXPT. 133. There is, as a rule, more moisture given off by the under 

 side of a leaf than by the upper. This can be proved by fixing the leaf 

 of the Oak or Beech with a piece of cobalt paper on each face and 

 enclosing it between slips of glass. Note 



The one fixed to the loA\;er side assumes the red colour far more 

 quickly than the one on the upper side. 



