SNOW- AND ICE-PLANTS. n 



as to look like nothing but an assemblage of tiny globules, 

 even when seen under the microscope, is still found, like 

 the plants of higher orders, to contain many minerals.* 

 The outer skin of the globule especially yields flint, nor 

 are lime, iron, and the other minerals essential to plant-life, 

 wanting. 



Another alga of a brownish-red colour, though closely 

 related to the red snow, is never found except on the ice, 

 where it grows in the blackish mud of the kryokonit 

 either on the surface or at the bottom of the deep holes 

 which, in the summer, pierce the ice in all directions to 

 the great inconvenience of explorers. 



These holes are indeed made by the alga itself, which 

 absorbs more heat than the surrounding ice, thanks to 

 its darker colouring, and thus it melts and sinks deeper 

 and deeper, until it is beyond the reach of the sunbeams. 

 Professor Nordenskjold even imagines that this microscopic 

 plant may have had the chief share in melting those vast 

 fields of ice which in a former age covered great part of 

 Europe and America. 



But the snow- and ice-plants serve other purposes be- 

 sides this. By feeding on the cosmic dust they convert 

 it into food capable of supporting animal life, and many 

 minute creatures, even in the Polar regions, are nourished 

 by the various, red, green, and brown algae, while the little 

 black " glacier-flea " lives almost entirely on the red snow 

 and its remains. 



In addition to the cosmic dust, the air is at times 

 charged with volcanic dust, the finer particles of which, 

 * See Chap. vii. 



