248 



ways in which leaves sometimes become fossiUzed, and carry us 

 back to the fossil leaf-beds which are so common in the Creta- 

 ceous of the coastal plain. The foregoing rivers carry much 

 sediment, especially during periods of high water, so that when 

 the raft finally becomes waterlogged and sinks in some quiet place 

 or is stranded on the sand-bars of some river cove like the one in 

 the center of the illustration, the river mud soon covers it and 

 we have an incipient clay bank with abundant leaf impressions 

 and layers of lignified leaves several inches in thickness. The 

 flood plains of these rivers, both ancient and modern, abound in 

 such leaf beds going back to the Pleistocene, if, indeed, it be pos- 

 sible to draw the line and say where the Pleistocene ended and 

 the recent deposits began. The leaves do not help us greatly in 

 this respect, for deposits of undoubted Pleistocene leaves are 

 practically all of species still existing, although in some cases 

 they may be of species not common to the region at the present 

 time, or the deposits may lack some of the common riverside 

 forms of the present. 



Unfortunately, good photographs were not secured of any of 

 these leaf-rafts in midstream, and the accompanying illustration 

 from a photograph taken on the Great Pee Dee river shows a 

 stranded raft which was about fifteen feet long and whose true 

 nature was carefully verified. It was still floating so that if the 

 background be eliminated a good idea is gained of the appear- 

 ance of these rafts. 



This is, of course, only one of the many methods by which leal 

 remains are stored away. The many swamps along the lower 

 reaches of these same rivers abound in beds of vegetable material 

 often many feet in thickness, and doubtless represent in a general 

 way the method of formation of the lignitic material in such for- 

 mations as the Montana and Laramie, as well as furnishing us 

 with a picture of the physical conditions and elevation of the land 

 during that period when the Mississippi gulf finally retreated from 

 the great interior region of the United States. They also serve 

 admirably to refute the now antiquated notion that peat is formed 

 only in high latitudes. 



Baltimore, Md. 



