80. 



OoT^c-jning the physics of the curling and ezcpanding 

 of the leaf of this epiphji-tic polypody, the writer believes 

 that the curling io not entirely an osmotic phenomenon. 

 The loss of water from the cell walls themselres probably 

 causes a shrinkage sind a deformation of the cell wall, The 

 so-called "resurection" of the leaves is probably largely 

 due to imbitionof water by the cell walls. Such seems clearly 

 true from the behavior of these walls as it v/as observed under 

 the microscope, in cross sections of fixed and imbedded leaves 

 where no osmotic action could occur, These cells, many of then 

 cut open 30 that turgor is impossible, expanded quickly to 

 their normal plump form upon the introduction of water, In the 

 living leaf , however, there is reason to believe that both 

 osmosis and imbibition aid in the expansion of the leaf 

 immediately after a rain.UndoubtedlJr, the process of expansion 

 then begins with an imbibtion of water by the cell walls and 

 later the osmotic action carries the v/ater from cell to cell 

 v/ithin the leaf thus aiding in the distribution of the water 

 imbibed by the cell walls. 



