60 THE PRESERVATION OF PLANTS AS FOSSILS. [CH. 



(fig. 6). There is little reason to doubt that at all events the 

 majority of the trees are in their natural place of growth. The 

 peaty soil on which they rest contains numerous flattened stems 

 of reeds and other plants, and is penetrated by roots, probably 

 of some aquatic or marshy plants which spread over the site of 

 the forest as it became gradually submerged. A lower forest- 

 bed rests directly on a foundation of boulder clay. Such sub- 

 merged forests are by no means uncommon around the British 

 coast ; many of them belong to a comparatively recent period, 

 posterior to the glacial age. In many cases, however, the tree 

 stumps have been drifted from the places where they grew and 

 eventually deposited in their natural position, the roots of the 

 trees, in some cases aided by stones entangled in their branches, 

 being heavier than the stem portion. There is a promising 

 field for botanical investigation in the careful analysis of the 

 floras of submerged forests ; the work of Clement Reid, 

 Nathorst, Andersson and others, serves to illustrate the value 

 of such research in the hands of competent students. 



The following description by Lyell, taken from his American 

 travels, is of interest as affording an example of the preserva- 

 tion of a surface-soil : 



" On our way home from Charleston, by the railway from Orangeburg, 

 I observed a thin black line of charred vegetable matter exposed in the 

 perpendicular section of the bank. The sand cast out in digging the 

 railway had been thrown up on the original soil, on which the pine forest 

 grew ; and farther excavations had laid open the junction of the rubbish 

 and the soil. As geologists, we may learn from this fact how a thin seam 

 of vegetable matter, an inch or two thick, is often the only monument 

 to be looked for of an ancient surface of dry land, on which a luxuriant 

 forest may have grown for thousands of years. Even this seam of friable 

 matter may be washed away when the region is submerged, and, if not, 

 rain water percolating freely through the sand may, in the course of ages, 

 gradually carry away the carbon i." 



In addition to the remnants of ancient soils, and the preser- 

 vation of plant fragments in rocks which have been formed on 

 the floor of an inland lake or an estuary, it is by no means rare 

 to find fossil plants in obviously marine sediments. In fig. 7 we 



1 Lyell (45), vol. i. p. 180. 



