60. 



PirrSICLOGICAL STTJDIES 



Tl?hile studying the effect of the climatic conditions 

 on the distribution of the polypody, the writer obseirved 

 carefully the peculiar curling of the leaves of this fern, 

 This characteristic "behavior of the leaves of Polypodium 

 polypodioides in dry v/eather seems at first sight to serve 

 as a special, adaptation against dessication,- 



Fig.20 



The polypody in wet 



weather with leaves 



expanded 



Fig. 21 



The polypody in dry weather 



with leaves curled up. 



The curling on drying begins, e.s a rule, by the rolling 

 inward of the pinnae from the ends with the upper surface 

 inward,As the entire leaf is folding, each individual pinna 

 also folds with its upper surface inward so that there 

 is really a double folding in each pinna, one main rolling in 

 endwise of each pinna towards the rachis and the other a 



