CH. VIl] 



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. Exp. 209. 



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

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



12—2 



