PLANTS OF THE SHINGLE BEACH = 39 
the open air only through narrow openings. The 
leaves of some of our common grasses show these 
characteristics to great advantage. And again the 
stomata are often sunk in little pits, by which device 
they obtain further protection. If we now examine 
the plants composing the sand-dune or shingle-beach 
associations in the light of these facts, we shall find 
them full of interest. The plants are well equipped 
to meet the adverse conditions of a very porous soil, 
drying winds, and scorching sun. Note the grey felt 
of hairs which protects the leaves of the Horned 
Fic, 5.—SECTION ACROSS INROLLED LEAF OF CROWBERRY 
(EMPETRUM NIGRUM), MUCH ENLARGED, 
Poppy (Glaucium flavum), the tough, waxy skin which 
covers the Sea Holly (Eryngium maritimum), the ex- 
tensive underground stem-systems of the fleshy-leaved 
Sea Convolvulus (C. Soldanella) and Sea Purslane 
(Honkenya peploides). Even the annual plants dis- 
play similar characters. In the great desert regions 
the annuals are often quite normal in structure: that 
is because they appear during the brief rainy season, 
and pass away before the fierce heat of summer sets 
in. But on our shingle beaches the annuals grow 
throughout the summer, and need protection against 
drought: so the Sea Rocket (Cakile maritima), the 
