318 



s. KUSANO : TKANSPIEATION OF 



designed by MacDougal^^ One arm (Fig. 1 a) of a T-sliaped 

 glass tube was bent parallel to the other arm ih) ; at the end of 



Fi^'- 1. 



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the former the branch was inserted, fitted with a rubber tube 

 and bound with wire for safety. From one end of the latter 

 arm, water was supplied by means of a stopcock, from the re- 

 servoir, while the other end of the same arm was connected with 

 the capillary tube which had an even inner diameter of nearly 

 one millimeter. After the apparatus was filled with water, taking 

 care not to leave any air bubbles in it, the loss of water absorbed 

 by the cut-surface and transpired from the surface of the leaves 

 was indicated by the diminution of the column of water in the 

 capillary tube. Tlie volume of the T-tube must not be too 

 large, since, if that be the case, a change of temperature gives 

 rise to a change of the volume of water which will consequently 



IjMacDougal, A convenient potometer. Bot. Gazette, Vol. XXIV, 1897, p. 110. 



