436 THE ECOLOGY OF PLANTS. 



their growth (Red Campion, Hemp Agrimony, Orchis, Blue- 

 bell, etc.). 



According to their position on rocks and cliffs, the plants 

 have to get a footing on almost bare rocks, or in loose soil in 

 crevices, or in sheltered nooks where the falling debris has 

 weathered into soil suited to shade-loving and hygrophilous 

 plants. The air is fairly moist owing to the cool breezes and 

 the frequency of fog and rain, but where there is exposure 

 to high winds and salt spray we get xerophilous plants like 

 the Scurvy-grass and Samphire. As a rule, however, typical 

 halophytes are not common on cliffs, though the beaches and 

 rocks at their bases often present the conditions suitable for 

 such plants, which grow most luxuriantly on sand near the 

 sea and in salt marshes. 



413. On sandy shores and sand dunes we get a fairly 

 large flora, varying greatly in different localities, and fre- 

 quently including rare (though often locally abundant) 

 species. 



On the sandy shore itself close to the sea, where the sand 

 is saturated with sea- water a little below the surface and 

 the latter is liable to become dry and hot in summer, there 

 grow such plants as Prickly Saltwort (Salsola kali, leaves 

 cylindrical and fleshy with a small sharp spine at the tip), 

 Orache (Atriplex, several species, often shrubby, with mealy 

 leaves and spikes of small green flowers), Sea Beet (Seta 

 maritima, with glossy ovate or lanceolate leaves), Horned 

 Sea Poppy (Glaucium) , Sea Convolvulus (spreading over 

 the sand instead of climbing like the other Bindweeds), Sea 

 Holly, Sea Purslane, Sea Kale, Sea Rocket, Sea Spurge 

 (Euphorbia par alias, with narrow fleshy leaves, milky juice as 

 in other Spurges), Sea Milk wort, etc. All these plants have 

 fleshy, hairy, or leathery leaves, and are either annuals, or if 

 perennial have long taproots or rhizomes, and are able to 

 grow upwards and thus avoid being buried by the shifting 

 sand. 



Sand dunes consist of ridges and hollows above the tide 

 limit, formed partly by water- currents (near the. sea) and 

 partly by wind (farther from sea). Near the sea the chief 

 plants found, besides those just mentioned, are certain Grasses 

 and the Sand Sedge, whose creeping stems and tufted roots 



