MEANS OF ACCELERATING TRANSPIRATION. 



2m 



round the edge of the disc, on account of which the drops of water roll down from 

 the middle of the leaf to the edge on the slightest rocking movement, and there 

 coalesce with the water on which the leaves float. 



This puckering .- " -;, 



of the margin of , 



the leaf is attended ; -^ t 



in the water-lilies 

 hy a phenomenon 

 which, although 

 not directly asso- 

 ciated with the 

 matter in hand, is 

 so full of interest 

 that it cannot be 

 passed without 

 notice. If we take 

 a boat in the bright 

 sunshine at mid- 

 day, and float over 

 the calm inlet of a 

 lake, whose surface 

 is overspread with 

 the leaves of water- 

 lilies, and if the 

 water is clear to 

 the bottom, we 

 shall see the sha- 

 dows of the leaves 

 which float on the 

 surface sketched 

 out on the ground 

 below. But we can 

 scarcely believe 

 our eyes — these do 

 not look like the 

 shadows of the 

 leaves of water- 

 lilies, but rather 



of the fronds of huge fan-palms. Fi'om a dark central portion radiate out long dark 

 strips which are separated from each other by as many light bands. The cause of 

 this peculiar form of shadow is to be found in the undulating margin of the floating 

 leaves. The water of the lake adheres to the whole of the under surface of the 

 disc as far as the edge, and is drawn up by capillarity to the arched portions 



Vui.. 1 19 



Fig. 63.— Cory2}ha umbracxtUfera of Ceylon (after Ransonnet). 



