128 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



attract water i.e. the osmotically active substances 

 of such a kind that they suddenly become less power- 

 ful, and can no longer retain their hold on the water, 

 which is therefore freed and escapes in the direction 

 of least resistance. Then the osmotically powerful 

 substances are restored, attract water, and again lose 

 their hold, and so on periodically. 



Now, as Godlewski points out, it has been shown 

 by De Vries that every time certain molecular decom- 

 positions occur in the cell, the attraction for water is 

 increased ; and it is extremely probable that periodic 

 changes of the following nature occur in the cell- 

 first, certain molecular combinations are built up which 

 have a definite power of attracting water osmotically : 

 then these molecular complexes undergo explosive de- 

 compositions under the influence of respiratory oxida- 

 tion, the larger number of molecules thus formed 

 having a more powerful osmotic attraction for water. 

 De Vries seems to have established, in fact, that with 

 each splitting of a complex compound into simpler 

 ones, the osmotic power of the cell is increased ; while 

 with each union of simpler into more complex mole- 

 cules it is lessened : and, again, with every solution 

 of a part of the protoplasm, the osmotic power in- 

 creases ; the reverse occurring each time an excretion 

 of insoluble substances occurs in the cell-sap. 



