94 HOUSE, GARDEN, AND FIELD 



crimped. The leaf-stalk is attached near the centre, and 

 behind this point the leaf is split. The special reasons 

 which bring about so great a variety of form in the leaves 

 of land-plants do not apply to floating leaves, which are 

 usually of very simple shape. They need no protection 

 from wind ; down-pointing cusps, such as drain off the 

 rain from many hanging leaves, would here be quite 

 useless ; all the leaves lie in one plane and are well exposed 

 to light. The chief accident to which they are exposed 

 is the sliding of one leaf over another, which hinders the 



FIG. 19. Yellow water-lily. Upper surface of rootstock. x . 



access of air and light to the lower leaf, and often causes 

 premature decay. Under natural conditions this accident 

 does not occur. Nymphaea is partial to deep waters, and 

 I have found it rooted at the bottom of a Highland loch, 

 in a depth of forty feet. Then the long, curved and 

 flexible leaf-stalks, like slack cables, allow so much play 

 to the leaves, that they can adjust their distances and 

 avoid mutual pressure. But when the plant is grown 

 in shallow water, it cannot avoid overcrowding. There 

 is not enough length of stalk for the leaves to adjust their 

 distances, and they sometimes push one another into the 

 air, or are pushed up by the undue elongation of the leaf- 

 stalk. 



