THE PERMEABILITY OP PROTOPLASM 



133 



TABLE XXXII. 



THEBMOTROPIC CURVATURES AND PERMEABILITY VARIATIONS 

 OP ROOTS. 



The interpretation of the results of this investigation 

 appears to be that, since there is such close agreement 

 between the temperature limits of thermotropic curvature 

 in a positive direction and increase of permeability, and a 

 similar relationship exists between negative thermotropism 

 and decrease of permeability, it is to be concluded that the 

 occurrence of curvature in any direction is due to the 

 diminished turgor of the cells on that side owing to their 

 increase in permeability. When the curvature is positive 

 the effect of heat is to increase permeability, for the cells 

 on the side next the source of heat are at a slightly higher 

 temperature than are those on the opposite side, and as a 

 consequence are more permeable and less turgid. When 

 a negative curvature takes place, it is because at the tem- 

 perature in question the effect of heat is to diminish per- 

 meability, and so the side remote from the source possesses 

 the smaller turgor. 



