CH. Vll] 



FROST. 



179 



room the leaves rapidly assume a normal position. The 

 droop is due to a sharp curvature in the petiole : if leaves 

 are cut and placed in lukewarm water the straightening 

 of the petiole occurs at once and is clearly visible 



FIG. 34. 



. 209. 



to the naked eye. Fig. 34 shows a laurel twig, A 

 in the frozen, and B in the thawed condition. It seems 



122 



