INTRODUCTION. 9 



tq Greenland, across the north of America, a stretch of 

 many thousands of .miles; all these immense areas of 

 the earth's surface where not a tree, nor a shrub, nor 

 a flower is seen, except the creeping arctic willow and 

 birch, and the stunted moss-like saxifrage and scurvy 

 grass are covered with fields of lichens and mosses, far 

 exceeding anything that can be compared in that respect 

 amongst phanerogamous plants. Thus, to the rugged 

 magnificence of Alpine scenery, and the dreary isolation 

 and uniformity of the Arctic steppes, and the boundless 

 wastes of brown desert and misty moorland, to these 

 great outlets from civilisation and the tameness of ordi- 

 nary life, which allow the soul to expand and go out in 

 sublime imaginings towards the infinity of God, these 

 humble plants form the sole embellishments. 



So much for the distribution of these plants on the 

 land ; their range in the waters is still more extensive. 

 Lichens and mosses cover the waste surfaces of the earth ; 

 diatoms and confervse are everywhere miraculously abun- 

 dant in the waters. In rivers and streams, in ditches 

 and ponds, alike under the sunny skies of the south, and 

 in the frozen regions of the north ; on the surface of the 

 sea in floating meadows, and in the dark and dismal 

 recesses of the ocean only to be explored by the long 

 line of the sounding-lead. The ocean swarms with in- 

 numerable varieties, without their presence being indi- 

 cated by any discoloration, of the fluid. The Arctic and 

 Antarctic Oceans, covering areas larger than the continents 

 of Europe and Asia, are peopled by myriads of diatoms ; 

 various inland seas and lakes are tinged of different hues 

 by their predominance in the waters ; while it has been 



