64 THE PRESERVATION OF PLANTS AS FOSSILS. [CH. 



Thunb., a low stemless palm that grows in the tidal waters of the Indian 

 Ocean, and bears a large head of nuts. It is a plant of no interest to the 

 common observer, but of much to the geologist, from the nuts of a similar 

 plant abounding in the Tertiary formations at the mouth of the Thames, 

 having floated about there in as great profusion as here, till buried deep 

 in the silt and mud that now forms the island of Sheppey^." 



Of the drifting of timber, fruits, &c., we find numerous 

 accounts in the writings of travellers. Rod way thus describes 

 the formation of vegetable rafts in the rivers of Northern British 

 Guiana : — 



"Sometimes a great tree, whose timber is light enough to float, gets 

 entangled in the grass, and becomes the nucleus of an immense raft, 

 which is continually increasing in size as it gathers up everything that 

 comes floating down the river 2." 



The undermining of river banks in times of flood, and the 

 transport of the drifted trees to be eventually deposited in the 

 delta is a familiar occurrence in many parts of the world. The 

 more striking instances of such wholesale carrying along of trees 

 are supplied by Bates, Lyell and other writers. In his descrip- 

 tion of the Amazon the former writes : 



" The currents ran with great force close to the bank, especially when 

 these receded to form long bays or enseadas^ as they are called, and then 

 we made very little headway. In such places the banks consist of loose 

 earth, a rich crumbling vegetable mould, supporting a growth of most 

 luxuriant forest, of which the currents almost daily carry away large 

 portions, so that the stream for several yards out is encumbered with 

 fallen trees, whose branches quiver in the current 3." 



In another place, Bates writes : 



" The rainy season had now set in over the region through which the 

 great river flows ; the sand-banks and all the lower lands were already 

 under water, and the tearing current, two or three miles in breadth, bore 

 along a continuous line of uprooted trees and islets of floating plants*." 



The rafts of the Mississippi and other rivers described by 

 Lyell afford instructive examples of the distant transport of 



1 Hooker, J. D. (91), p. 1. There are several good specimens of the black 

 pyritised nipadite fruits in the British Museum and other collections. 



2 Eodway (95), p. 106. '^ Bates (63), p. 139. 

 ^ Bates (63), p. 239. 



