Problem of Xeromorphy in Marsh Plants . 825 
Some of the more important features may now be dealt with in detail. 
(a) The stomata . These are slightly raised, even in the more exposed 
leaves of 5 . Ulmaria , var. denudata (Text-figs. 3 and 4). They are for the 
13 6 10- .15 16 is 21 
most part confined to the lower surface of the leaf. The only exceptions to 
this are (1) a few at the sides of the larger veins, and (2) groups of very 
small stomata, which are crowded on the upper surface of the leaf-teeth, 
immediately above the endings of the more important veins. On determin- 
