LEAVES 



545 



since it doubtless results in the greatest food production possible within 

 a given volume of leafage. In many swamp plants, verticality is not 

 due entirely to leaf crowding; in various monocotyls (as Typha) the 

 leaves are enclosed in sheaths, and in the rushes {Juncus, Scirpus, 



Fig. 783. — A colony of the bur-reed {Sparganium eurycarpum); the sunlight 

 reaches the leaves at all depths, in spite of their dense arrangement; closely placed 

 vertical leaves permit a maximum of lighting for vegetation as a whole, though the amount 

 received by each leaf is relatively small; a water lily {Castalia) is seen in the foreground. 

 Miller, Indiana. — Photograph supplied by Meyers. 



Eleocharis) the stems rather than the leaves often are the chief foliage 

 organs (p. 666). 



Forest undergrowth. — The relation of light to foliage is particularly evident in 

 forests. The luxuriant undergrowth of open sunny oak woods often contrasts 



