280 The American Naturalist. [April, 



forces to prevent the motion of the water which would other- 

 wise sink. In other words, the sole function of the chain is to 

 prevent the water from yielding to the action of the gravity. 

 In this way according to the distribution and tension of the air 

 bubbles, the water is more or less evenly distributed through- 

 out the whole stem of the tree and is ready for use whenever 

 needed at different altitudes. The next step in the problem 

 is to discover the factor by which the water is drawn out and 

 set in motion upward. It is here that Professor Schwendener 

 differs from nearly all the younger men who adhere even too 

 zealously to his cause. In short, the last set of experiments 

 which he made were for the purpose of disproving the claims 

 of those who consider themselves able to follow all the succes- 

 sive forces which act in sending the water upward from the 

 root hairs to the transpiring leaves. The question of lumen 

 versus wall was not at all touched by these experiments. On 

 the other hand, they were made to test the length of alternat- 

 ing air and water columns, diameter of tube, etc., and from 

 these results a series of mathematical computations was made, 

 it is true from data more or less uncertain, but yet with such 

 allowances for extreme cases as to prove conclusively that 

 some other force was necessary than those held sufficient by 

 his contemporaries. 



Pieces of wood were taken from the inner portions of the 

 trunks of various trees, with apparatus allowing perfectly air 

 tight processes. The pieces were transposed from the tube of 

 the borer into glycerine or water from which all air had been 

 expelled. From these computations it was shown that in no 

 case would it be possible for the action of suction caused by 

 the evaporation from the leaves to reach down much below 

 the crown of the tree, and in case of trees with trunks from 50 

 to 100 metres long this might he considered proof against the 

 possibility of the force reaching downward until it reaches that 



effected below by the foi 



ees acting in the lower part of the 



tree. The whole labor if 



; merely i„ disprove certain theories 



not to establish new one: 





In conclusion Profess,. 



r Schwendener sayi the results agree 



