THE PAGE OF NATURE. 79 



ference, Mrs. Somerville observes, appears to arise " more 

 from the want of warmth in summer, than from the 

 greater degree of cold in winter." The portion of heat 

 imbibed by the soil, during the short summer of the 

 Arctic regions, is prevented from escaping by the cover- 

 ing of snow which falls in the beginning of winter ; and 

 thus the temperature necessary for the scanty vegetation 

 is preserved, till the return of the sun at once converts 

 the Arctic winter into tropical summer, without the in- 

 tervention of spring. Whereas in the Antarctic regions, 

 the soil, owing to the much smaller quantity of snow 

 that lies on it, is exposed to great alternations of tempera- 

 ture, which no vegetation, however simple and tenacious 

 of life, can long successfully resist. 



In the deserts of Asia and Africa, and on the coast of 

 Peru, botanists have wandered for many leagues, without 

 finding any other trace of vegetation, than a species of 

 grey or yellow lichen, growing on the blanched and 

 mouldering bones of animals that had perished by the 

 way. In tropical countries, where there is not too much 

 moisture and shade, the trees are shaggy with lichens ; 

 and some of the most magnificent species, both as re- 

 gards size and colour, have been gathered in the Cin- 

 chona forests which clothe the lower slopes of the Andes, 

 and in the warmer and more densely-wooded parts of 

 Australia and New Zealand. The thick impervious 

 forests of Brazil, however, are said to be almost destitute 

 of them ; their places on the trunks and boughs of the 

 trees being occupied by endless varieties of ferns, til- 

 landsias, orchids, and other epiphytic plants, which seem 

 to hold a floral revel ; the amazing luxuriance of higher 



