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THE ESSEX NATURALIST. 
found in land plants ; the water-conducting woody tissue is 
much reduced ; the temperature in which the plants live is fairly 
equable, encouraging free growth, which the abundant supply 
of carbon dioxide dissolved in the water also favours. In order 
to take advantage of all possible light filtering down through 
the water, the epidermal cells often contain chlorophyll, which 
is never the case with flowering plants on land ; there are no 
stomata, or none that are functional ; to provide a supply of 
air and ensure aeration a complete system of air chambers is 
developed amongst the tissues. The leaves are buoyed up by 
this means and brought nearer the light. In shape, these ribbon 
leaves are well adapted for life in slow streams ; they bend with 
the current, offering little resistance to it, and therefore are not 
liable to be injured by the flow of water. 
But the time comes when the needs of the Water Plantain 
grow beyond that afforded by the ribbon-leaves ; long-stalked 
leaves are then produced with small oval blades, which often 
float on the surface of the water. These floating leaves have 
a similar structure to those of aerial leaves, except that their 
stomata are all upon the upper surface. Later still, stronger 
and completely aerial leaves are formed, with stiff stalks and 
erect blades six to eight inches long ; and finally the inflores¬ 
cence is produced. Like most of our water plants the Water 
Plantain is perennial. In autumn, starch is stored in the stout 
