128 I. i. RUSSELL — SI IMAM. GEOLOGY OF A.LASKA. 



The flora of the tundra, however, like the plants of the Carboniferous, is 

 essentially and characteristically cryptogamie. Two species of Equisetum, 

 which maybe considered a- representing tin- Calamites of former times, 

 flourish with rank luxuriance over great areas along the Yukon. 



It' the tundra-friDged coasl of Alaska should subside, the peaty layer with 



which it is covered would be< le buried beneath Bands and clays, ami form 



a stratum in every way favorable for transformation into lignite and coal. 

 The plant ami animal remains associated with it would indicate the climatic 

 conditions under which ii accumulated, hut the overlying Bandstones ami 

 shales might also carry leaves ami tree trunks transported by rivers from 

 warmer regions. 



Lakes on Hi' Tundra. — The surface of the tundra, as already mentioned, 



i- frequently diversified by | Is and lakelets. Moat of these have no definite 



nutlet, bul are c< mi ] -let el y surrounded by luxuriant hanks of moss, through 

 which the water escapes as through a sponge. The moss encroaches on the 

 lakelets from all side-, and finally completely covers them in the same man- 

 ner as the Sphagnum increases about the borders of ponds in the peat hogs 

 of New England and other temperate regions. As the moss covers the lake- 

 let- more and more completely during a series of years, the ice formed by 

 the freezing of the water in winter i- more and more thoroughly protected, 

 ami 18 finally completely shielded from tin; heat of summer. A body of 

 clear ice is thus formed in the tundra, similar to the Btrata of ice exposed at 

 certain localities along the coast of Behring sea and in the hanks of the 

 Yukon. 



This explanation of the presence of clear ice in the tundra has previously 

 been Bl I bj I.. M. Turner in the introduction to his report on the 



natural history of Alaska, already referred to. A similar explanati f 



the presence of thick beds of clear ice in the cliffs bordering Eschscholtz 

 bay has been recorded by E. \V. Nelson and ('. L. Hooper,* together with 

 an alternative hypothesis to the - Hi ct thai the ice mighl have resulted from 

 tin- freezing of water which filtered through the surface layer of moss. 



Stratified I" '» tin Tundra.- The great Dumber of lakelets on the surface 

 of the tundra renders it evident that if their extinction ami the consequent 

 burial of ice beneath the Burface lake- place in the manner Bupposed Bheets 

 of ice, probably more or I- -- lenticular in Bhape, should form a characteristic 

 i. ature of tundra deposits. The origin of the lakelet- may perhaps he due 

 to tic accumulation of snow hank- on the tundra, which by their late melt- 

 ing enable the me-- surrounding them in grow more rapidly than on the 

 more deeply covered area-. In this way a depression in the surface would 



l.e formed which WOUld he flooded after the -lluU melted. A lakelet mice 



' orw in, in ii,- 

 Dgton, 1884, p 



