180 MONOCOTYLEDONS 



{a) Fixing in the soil. — Not only are various stocks con- 

 nected with one another by strong runners, but they are also 

 strongly fixed in the sand by numerous, deep roots v/hich some- 

 times attain the length of ten feet and more. 



(b) Supply of ivater. — The roots penetrate the sandy soil in 

 every direction and reach a depth where the soil is always wet. 

 Thus the plant is supplied with water. But that water is saltish. 

 If much salt is absorbed, the growth of the plant is hindered 

 (see Mangrove, page 53). The leaves, therefore, have not only 

 a large water-storing tissue in them, which keeps the solution of 

 salt at a low percentage, but they are also protected against a 

 great loss of water through transpiration by means of that bluish 

 coat of Avax spreading over the epidermis. 



(c) The plant and the wind. — Such a xerophilous structure is 

 also necessitated by its constant exposure to strong breezes. 

 For the same reason it must be strongly rooted in the loose sand, 

 as seen above. As the plants are not tall, the wind can do 

 them very little harm. On the contrary, they take advantage 

 of the wind in letting it tear oft' the mature globular fruits from 

 their dried stems. Rolling and dancing, the fruit-balls are 

 carried away over the smooth sandy plain, dropping one seed 

 after another on their way. By and by, the bristles between 

 which the seeds lie, are worn away, and they are finally buried 

 under the sand with the rest of the seeds. 



7. The Distribution of the Grasses.— We have seen that 

 the greater part of the food of man is derived from plants be- 

 longing to the family of the Grasses. It is, therefore, no matter 

 of astonishment to learn that the (Jrasses, such as Rice, Wheat, 

 Millets, cover the larger part of our cultivated areas. Grasses 

 form the extensive meadows spread out over hills and dales; they 

 inhabit the soft swamps as well as the beaten ground of the way- 

 side; they thrive in the cool shade of jungles and on the 

 scorched heath, on the sandy soil of coast tracts and on the rocky 

 ground of mountains, in the arctic zone under snow and ice, as 

 well as in the torrid zone under the parching heat of the sun; 

 they form the extensive tracts known as the Prairies in North 

 America, the Pampas and Llanos in South America, and the 



