MEANS OF ACCELERATING TRANSPIRATION. 



289 



^ -:* 



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m\ 



lirnu .■ 



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 



in the water-lilies 



by 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 

 I leaves of water- 

 I lilies, but rather 

 I of the fronds of huge fan-palms. From a dark central portion raaiate 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 



arched portions 



19 





Fig. es.-o- 



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



Vol. I. 



the 



