362 SCIENCE PROGRESS 



been brought to light. The fallen leaves, twigs, branches, and 

 tree-trunks of the Coal Measure forests seem to have been 

 quickly plunged into free water, and thus to have become 

 thoroughly soaked. They further appear to have been carried 

 by streams into salt lagoons 1 or lakes, and there to have been 

 finally deposited. At the present day such conditions are found 

 to be very unfavourable to the wood-destroying fungi. The 

 mycelium of these organisms does not seem able to develop in 

 wood which has its cell-lumina filled with free water. Wooden 

 piles, submerged beneath either fresh or salt water, remain long, 

 if not entirely, protected from fungi. Thus the piles in the lake 

 dwellings of Switzerland and Ireland have lasted for centuries. 

 When the piles of Old London Bridge 2 were taken up they were 

 found to be sound after six hundred and fifty years of use. 

 Complete saturation of wood with water, which now preserves 

 timber from the inroads of fungi, was in all probability just as 

 unfavourable to these organisms in the Carboniferous Period. 

 When this is admitted it is easier to understand the accumulation 

 of the materials which have formed the coal seams. 



Among the agents at present at work in destroying wood, 

 animals will first be shortly considered. When compared with 

 plants, however, they play but a subordinate part in the great 

 process. 



Almost all the higher animals leave wood untouched, if for 

 no other reason, because its mechanical resistance defies their 

 teeth. A few rodents have the habit of gnawing wood, partly 

 for the purpose of making burrows in which to live or hide, and 

 partly in order to obtain food. The enormous annual destruc- 

 tion of wood, including standing timber, by fire through the 

 agency of man is, of course, a matter of common knowledge. 

 Charred wood, found by palseobotanists in rocks which were 

 formed before man had been evolved, indicates that forest fires 

 have originated in the past by lightning or spontaneous 

 combustion. 



Certain Crustacea of the group Malacostraca, e.g. Chelura 

 terebrans? bore into wood piles and thus weaken them. Some 

 Molluscs of the group Lamellibranchiata, e.g. Teredo navalis, the 

 " ship-worm," have the same habit. By boring into piles the 



1 Geikie, Text-book of Geology, 3rd ed., p. 805. 



2 G. S. Boulger, Wood, 1902, p. 254. 



3 R. Hertvvig, Lehrbach d. Zoologie, 4 te Aufl. p. 386. 



