IV] VARIOUS THEORIES, &C. 139 



transpire and to raise water to heights far above that 

 of the barometric column, even though poisonous 

 substances are dissolved in the water supplied to the 

 roots. Consequently it is impossible to maintain 

 Godlewski's hypothesis in the form put forward. 

 Strasburger's work renders it probable that the 

 columns of water in the vessels and tracheids of the 

 sapwood are not broken by air bubbles, but are 

 continuous filaments of water reaching from root to 

 crown, at any rate in the newest and most active 

 wood, or, in Conifers, only incompletely broken by the 

 septa of the tracheids. In view of these and other dis- 

 coveries which Strasburger finds it impossible to recon- 

 cile with Godlewski's theory, we are driven to believe 

 that, after all, the ascent of water in wood is more 

 of a physical phenomenon than has been supposed. 

 This becomes more probable in view of Dixon and 

 Joly's recent work at this difficult subject, for they make 

 it appear probable that just such columns of water 

 as Strasburger maintains exist in the wood can be 

 raised by the osmotic pull exerted by the cells of the 

 transpiring leaves, and will not break under the strain, 

 owing to the power of resisting tensile stress possessed 

 by liquids. This point of view, introduced for the 

 first time by Dixon and Joly, and independently 

 confirmed subsequently by Askenasy, had been 

 entirely overlooked, partly owing to difficulties in the 



