34 THE BOOK OF NATURE STUDY 



a real or imaginary mountain ascent, so an excursion to the 

 shore, elevated in imagination to a desert journey, will yield much 

 that is of value. Almost all the essential points in regard to 

 desert conditions are illustrated on many parts of our own coast- 

 line. 



One would, of course, point out that although the same rain 

 falls on the shore as on the green fields or woods inland, yet the 

 fact that the sand is excessively porous produces a condition 

 of drought analogous to that which obtains in the Sahara or 

 many parts of America where the rainfall is very scanty. Let 

 the members of the class examine the fleshy-leaved sand spurrey 

 and other shore plants, noting the long roots which these send down 

 into the shifting sand in search of water. While they are looking 

 at these speak to them of the great cactuses of the American 

 deserts, and let them reconstruct that desert in imagination. 

 Show them the creeping sand-reed (Ammophila arundinacea) 

 with its curled-in leaves, and explain how it binds the sand and 

 makes a beginning of vegetable mould of which other plants are 

 quick to take advantage. Show them how as we pass inwards 

 from the shore the sand loses its golden colour, becomes darker 

 and more soil-like, and that as it becomes soil-like more and 

 more different kinds of plants can grow upon it. Explain 

 that the dark matter in the sandy soil (humus) has the power 

 of holding water, and that where it is present at the surface 

 the water does not run through as it does through the pure sand. 

 To make a desert sandhill a grassy field, then, we want first to 

 stop the sand shifting with the wind, and this is done in nature 

 by plants with creeping rootstocks. Second, we want to add 

 some water-holding substance to the soil, to prevent the abundant 

 rainfall from running through the sand. This is done in nature 

 by the first hardy plants that get a foot-hold on the sand, which 

 by their dying leaves, by the small plants that accumulate round 

 their roots, add vegetable matter to the sterile sand. If these 

 two conditions can be fulfilled, and there is no excessive amount 

 of salt in the sand, the dune gradually passes into fertile land. 

 But this is because in our country there is abundant rainfall, 

 and with the help of that rainfall the sand-reed conquers the sand 

 from the ocean, to be conquered in its turn by the other plants which 



