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 Poppy (_Glaucium flavum_), the tough, waxy skin which covers the Sea Holly (_Eryngium maritimum_), the extensive underground stem-systems of the fleshy-leaved Sea Convolvulus (_C. Soldanella_) and Sea Purslane (_Honkenya peploides_). Even the annual plants display 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 Sea Whin (_Salsola kali_), and others are very fleshy plants; their leaves are small, with an impervious skin, their root-systems are better developed than in most annuals. The grasses and sedges of these places, such as the Bent (_Ammophila arenaria_), Sea Wheatgrass (_Triticum junceum_), Sea Sedge (_Carex arenaria_) have underground stems which burrow widely through the sand, with an extensive root-system, and tufts of inrolled leaves beautifully protected against over-transpiration and well worth microscopical examination.