172 Biology in America 



winjred butterfly may be found flitting over the barren lands 

 of the Arctic and the highest mountain peaks. Many other 

 types of insects may also be found here. 



Over the ice and snow fields of the Arctic the polar bear 

 holds sway, the mortal enemy of the seal, while the arctic 

 fox plays the part of a hanger-on at court, feasting upon 

 the remains of seal which <lrop from the royal table. Over 

 the tundras of the barren lands, covered with an abun- 

 dant vegetation in the brief summer, roam the musk ox and 

 the barren ground carilxni, while the arctic hare, the mar- 

 mot and the lemming or northern mouse, find a table plen- 

 tifully spread with roots and grasses. 



The Woodchuck 



Photo by Eltcin R. Sanhorn. 

 Courtcmj of the Neic York Zoological Society. 



Descending from the barren summit of the mountain to 

 timber line one encounters the outposts of the forest at an 

 altitude of 11,500 feet in the form of stunted spruce and pine, 

 "whose gnarled and weather-beaten forms bear testimony to 

 the severity of their struggle with the elements." 



Below timber line one comes to a rather indefinite zone 

 characterized by spruces and fox-tail pines. IMany of the 

 plants characteristic of this zone on San Fi'ancisco Mountain 

 are represented by the same or closely related species in the 

 "upper spruce belt of the higher Alleghenies, the Rocky 

 Mountains, the Cascades, and the Sierra Nevada, and ... the 

 great northern spruce forest of Canada." Here live several 



