GERMINATION, GROWTH, TISSUE TENSION. 161 



and record the lengths. Then cut off the epicotyl, and plasmolyse 

 it with 10 per cent, salt solution. On a piece of cork or soft wood 

 make two marks corresponding to the length of the marked portion 

 of the epicotyl. Lay the plasmolysed epicotyl on the cork, so that 

 the highest ink mark on it corresponds with one of the marks on 

 the cork. Hold this end of the epicotyl down, and pull at the 

 other end so as to bring the lowest ink-mark on the epicotyl to the 

 other mark on the cork. Pin the stretched epicotyl to the cork, 

 lay alongside it a scale, and measure off the lengths of the zones. 

 Note that the tissue is more extensible in the younger than in the 

 older zones. 



The result of this experiment shows that there is a direct relation 

 between the rate of growth, the amount of turgor tension, and the 

 extensibility of the tissue in the different zones. 



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