190 LEAVES FROM THE BOOK OF NATURE. 



cool evening comes, and rich dew pearls in the morning 

 on the meadows, and refreshes the fields. Trees thus affect 

 materially the climate and general character of countries. 

 Thickly-wooded regions, like our own continent, are colder 

 and more humid than cultivated or broad treeless savan- 

 nahs ; they abound in rain and fertile dew ; and to cut 

 down our trees is seriously to impair the supply furnished 

 by them to springs and rivers. Some lands would not 

 be habitable but for trees. In one of the Canaries neither 

 springs nor rivers are found ; but there grows a large, 

 tall tree, called with veneration the Saint, in some of the 

 deep recesses of the mountains. It keeps its lofty head 

 all night long wrapped up in mist and clouds, from which 

 it dispenses its timely, never-ceasing moisture in little 

 rivulets, running merrily down from the leaves. Small 

 reservoirs are built for the purpose of catching the pre- 

 cious gift, and thus alone the island is made a fit dwelling- 

 place for man. 



Humbler plants store up water in smaller quantities, 

 but not the less pure or welcome. The melon cactuses 

 have been called the vegetable fountains of the desert, 

 because they conceal under their hideous prickly envelope, 

 covered with dry lichens, an ample supply of watery pith. 

 The great Humboldt tells us graphically, how, in the dry 

 season, when all life has fled from the pampas, and even 

 snakes lie buried in the dried-up mud, the wild mule, per- 

 ishing with thirst, gallops up to the ill-shapen plants, strikes 

 with its hoofs at the powerful prickles, until it has made 

 an opening, and then warily approaches, with long pro- 

 truding lips, to drink the well-defended, cool and refresh- 



