1 88 



The Living Plant 



crosswise. The basis of this fact is not known, but I venture to 

 suggest as a possible explanation that the sides of the cubical 

 micellse facing towards the end of the wood (those towards and 

 away from the reader in the sections of figures 59 and 64) have 

 no attraction for water at all, and hence absorb none; and this 

 view I propose that we hold as an hj^pothesis until it is disproven 



Fig. 64. — A diagram illustrating the molecular basis of the warping of wood. It belongs 



between a and b of figure 59. 



or a better is offered. The supposition that micellar surfaces can 

 exist without any attraction for water will help also to explain 

 how cell-walls can be waterproof, as they actually are in cork 

 and epidermis. 



A special form of imbibition by dry tissues is the absorption 

 of water vapor from moist air, with its return thereto as the 

 ^ir becomes dry, — a phenomenon called hygroscopicity. Fa- 

 miliar examples occur in the softening and sagging of paper in 

 damp weather, in the uncurling and curling of hair, in the move- 

 ments of the wood of old furniture, giving rise to snappings and 

 creakings which are oft of uncanny effect when heard in the 

 stillness of night. Now, in essence, hygroscopic movement is the 

 same thing as warping, the water being absorbed as a vapor 

 instead of as liquid. Furthermore, if the tissues are made \'ery 



