56 THE HARMONIES OF NATURE. 



As under the shelter of the Laminaria3 r thus also a host of 

 marine animals and plants live and flourish under the green 

 carpet of the submerged meadows of the Zostera, and thus in 

 both cases the existence of a little world ultimately depends 

 upon the peculiar structure of the roots of the protecting 

 plant. 



Ascending from these 'submerged forests and meads to the 

 sand-dunes which on many flat coasts oppose an invincible barrier 

 to the stormy ocean, we here also find plants eminently adapted, 

 by the structure of their roots, for flourishing on a loose and 

 drifting soil. Of these the sand-reed (Ammophila arundinacea), 

 which naturally grows on the sandy shores of Europe, is one of 

 the most remarkable. Its roots penetrate to a considerable 

 depth, ramifying in all directions and forming a complete system 

 of rope-work, which soon binds together the loosest sands and 

 firmly attaches the plant, while its strong tall leaves protect the 

 surface of the soil from drought, and afford shelter to small 

 plants, which soon grow between the reeds, and gradually form 

 a new green surface on the bed of sand. 



But for the sand-reed the sea-winds would long since have 

 wafted the drift-sand of the dunes far into the interior of the 

 country, and converted many a fruitful acre into a waste ; but 

 that invaluable grass opposes its stubborn resistance to the most 

 furious gale. Like a radical democrat, the wind would willingly 

 reduce all to one common level, but the Ammophila, an obstinate 

 conservative, opposes an indefatigable resistance to its fury, and, 

 after a war of centuries, still lines the flat coast with long undu- 

 lating chains of protecting sand-hills. 



In the deserts and steppes of South Africa we also find a 

 number of plants peculiarly fitted, by the formation of their 

 roots, for the arid soil on which they grow and flourish. Thus 

 creepers abound, which, having their roots buried far beneath 

 the surface, feel but little the effects of the scorching sun. Those 

 having tuberous roots are particularly abundant, a structure 

 evidently intended to supply nutriment and moisture to the 

 plant when, during the long droughts, they can be obtained 

 from no other source. 



In his description of the Kalahari desert, Dr. Livingstone 

 mentions one of these plants, named Leroshua by the native 

 Bechuanas. It has linear leaves and a stalk not thicker than a 



