1906.] 



On the Transpiration Current in Plants. 



57 



7-0 



6-0 



5-0 



4-0 







I-O 



• 



































/'' 

















S 



* 

















* 

















s 

















<! 



f' 





































\ IO 12 



Units Head. 

 Fig. 5. 



14 



16 



id 



20 



fall h to the ground. With regard to the soundness of the cohesion-theory 

 itself, apart from the weighty evidence which has elsewhere been adduced in 

 its favour,* the fact that other theories, both old and new, have to assume 

 properties for the water-ways of plants which are either in the highest 

 degree improbable according to received scientific views, or are even directly 

 negatived by experiment, seems to support the theory by a process of 

 exclusion. 



* Dixon and Joly, "Ascent of Sap," ' Phil. Trans.,' B, 1895; Dixon, " Physics of the 

 Transpiration Current," 'Notes from the Botanical School, Trinity College, Dublin,' 

 May, 1897. 



