I. Lesquereux on the Origin and Formation of Prairies, 328 
are such traces of marine action in Iowa and Minnesota in the 
timbered Coteaux, as the Coteau des Bois, Les Bois-rouges, etc., 
which cut the nakedness of the prairies and resemble those nar- 
tow strips of land bordering the ocean and soon becoming Jong 
_ peninsulas covered with a luxuriant arborescent vegetation. The 
_ tist origin of these undulations may have been in deep water, 
orthey may have resulted merely from the action of the waves. 
— Inany case, they cannot be compared with the barren knolls of 
: slagnant water, whenever water is low enough to admit the trans- 
‘Mission of light and air in sufficient quantity to sustain vegetable 
( lite the bottom is first invaded by Confervas, especially by Cha- 
Mee and a peculiar kind of floating moss (Hypnum aduncum 
_-ttdw.). These plants contain in their tissue a great proportion 
; of silica, lime, and even oxyd of iron.” Moreover, they feed a 
_ ‘Modigious quantity of small mollusks, whose shells add to the 
i 
I 
3 : 40 attributes to the decomposition of Confervas, Characez, etc., 
ca over which peat bogs generally rest. I have seen it in 
¢ 
‘the lakes of the high prairies it has sometimes a peculiar 
ter. At tha, dept Pe gine one to three feet, the plants 
to atmos- 
~Vandolle Physiologi 183 and 188. When exposed Se 
influence, the Case testes avail with an efflorescence of scarcely carbon 
te ime, 
