The weasels of the north (which turn white in winter and are then called ermines) are agile little 

 predators that keep down the hordes of lemmings and other rodents. 



expanding, and has reached equilibrium. There are only a few 

 such horsts on the surface of the earth — others are in Scandi- 

 navia, eastern Siberia, and. it now seems. Antarctica. They are 

 all very rich in mineral veins. 



THE REMARKABLE LICHENS 



Lichens are in many respects the most remarkable of all plants. 

 They are among the first living things to appear after any part 

 of the surface of the earth has been scoured by anything from 

 an icecap to a landslide, and they are the last to go when con- 

 ditions deteriorate to the point of death for all others. It is true 

 that the first living things to reach an utterly denuded and 

 devastated area are not always lichens but most usually spiders; 

 thus, for example, after the island of Krakatoa blew up. spiders 

 turned up on lava beds before they were cool, prior to any 

 reported plants. Very few air-breathing animals of a purely 

 terrestrial nature have been found in the Antarctic, but lichens 

 grow on almost all exposed rocks there, and lichens occur right 

 up to the tops of the highest mountains. The other astonishing 

 thing about lichens is that there is actually no such plant as a 

 lidien; all of them are combinations of two plants — an alga (the 

 seaweed group) and a /uMgM5— growing in most intimate asso- 

 ciation and according to their kinds, eadi combination in its 

 own form; yet both fungus and alga can often get along alone 

 and eadi looks entirely different from the other. Strangest of all 

 is that some of these combinations grow into very complex 



structures, sometimes surpassing any alga or fungus in this 

 respect. The underlying process is more like that of the "growth" 

 of human artifacts than the true growth of a plant — more like 

 cooking, by which a cake may be produced out of the more or 

 less haphazard mixing of various unlike ingredients and sub- 

 jecting the result to some heat. Lichens are the basis of the entire 

 Arctic economy of both man and beast, for there are actually 

 two lines of life that start with them and are dependent upon 

 them, one great, the other small. 



The first starts with the Barren Ground Caribou or American 

 Reindeer, which subsist to a very large extent on lichens, espe- 

 cially during the winter on the Ungava tundras. The only large 

 predator is the Wolf, though the Polar Bear is found all around 

 the coast and sometimes wanders quite far inland. The Black 

 Bear does not even venture out onto the tundra, and the dish- 

 faced or "brown" bears are of course a purely western form. The 

 only other animal that may take the young of the caribou is the 

 Wolverine, which is here quite common. The other food cycle 

 starts with those curious little rodents called the lemmings, on 

 which all the small predators appear to rely almost wholly. 



THE LEMMINGS 



There are two distinct species of lemmings on the tundra and 

 two more in the taiga. The Common or Brown Lemming 

 (Lemmus trimurcronalus) is a small brown rodent about five 

 indies long with only an apology for a tail. Its head is slightly 



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