BOEHM' S THEORY. 137 



the leaves of the plant. The part which he attributes to 

 the cellules, of which the organs are composed, he thus 

 describes: "When the superficial cellules of the plant 

 lose water by transpiration," he says, "of two things, one 

 will happen : either these cellules will contract and shrivel, 

 or they carry up, by a kind of aspiration, to the neighbour- 

 ing cellules, situated in deeper layers, a quantity of water 

 equivalent to what they had lost. In the normal condition, 

 the latter is always the result; each cellule takes from its 

 neighbour what itself has lost, and this action, becoming 

 more and more general, is continued from the leaves to 

 the extremities of the roots. The cellules of the spongioles 

 replace the water which they have yielded, from the humid 

 medium surrounding them." 



In support of this theory,* M. Boehm has made several 

 experiments, which, we fear, will not carry conviction to 

 every mind. 



In the different theories which we have been attempting 

 to explain, their authors, as it seems to us, have neglected 

 an essential element the life of the plant. Then, the 

 experiments undertaken by way of proof, have been made 

 upon cut stems or branches, which, consequently, did not 

 enjoy their integral vitality. In fact, the results indicated 

 could just as well have been obtained with inert as with 

 living matter. 



* Boehm, " Sur la Cause de 1' Ascension de la Seve," Memoire commu- 

 nique a 1' Academic des Sciences de Vienne, juillet 1863. 



