58 THE PRESERVATION OF PLANTS AS FOSSILS. [CH. IV 



land surface preserved in a different manner, reference may be 

 made to the thin bands of reddish or brown material as well 

 as clays and shale which occasionally occur between the sheets 

 of Tertiary lava in the Western Isles of Scotland and the 

 north-east of Ireland. In the intervals between successive 

 outpourings of basaltic lava in the north-west of Europe during 

 the early part of the Tertiary period, the heated rocks became 

 gradually cooler, and under the influence of weathering agents 

 a surface-soil was produced fit for the growth of plants. In 

 some places, too, shallow lakes were formed, and leaves, fruits 

 and twigs became embedded in lacustrine sediments, to be 

 afterwards sealed up by later streams of lava. In the face of 

 the cliff at Ardtun Head on the coast of Mull a leaf-bed is 

 exposed between two masses of gravel underlying a basaltic 

 lava flow ; the impressions of the leaves of Gingko and other 

 plants from the Tertiary sediments of this district are excep- 

 tionally beautiful and well preserved ^ A large collection 

 obtained by Mr Starkie Gardner may be seen in the British 

 Museum. 



In 1883 the Malayan island of Krakatoa, 20 miles from 

 Sumatra and Java, was the scene of an exceptionally violent 

 volcanic explosion. Two- thirds of the island were blown away, 

 and the remnant was left absolutely bare of organic life. In 

 1886 it was found that several plants had already established 

 themselves on the hardened and weathered crust of the Kraka- 

 toan rocks, the surface of the lavas having been to a large 

 extent prepared for the grow^th of the higher plants by the 

 action of certain blue-green algae which represent some of the 

 lowest types of plant life I We may perhaps assume a some- 

 what similar state of things to have existed in the volcanic 

 area in north-west Europe, where the intervals between suc- 

 cessive outpourings of lava are represented by the thin bands of 

 leaf-beds and old surface-soils. 



On the Cheshire Coast at Leasowe^ and other localities, 

 there is exposed at low water a tract of black peaty ground 

 studded with old rooted stumps of conifers and other trees 



1 Gardner (87), p. 279. ^ Xreub (88). 



3 Morton (91), p. 228. 



