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 eur year punt); 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 



