THE PHYSICAL GEOGRAPHY OF THE PAST. 
285 
sentatives. The ferns were mostly of the herbaceous kinds, 
but some large Tree Ferns also existed, far outstripping in 
height the noble Tree Ferns of our tropical islands. We look 
in vain for the higher orders of the flowering plants, for the 
Phanerogams were only represented by their lowest order the 
Gymnospenns, which included some Conifers, and a few 
Cvcads. These dense and tangled brakes were not without; 
animal life, for we have found in the Coal Measures remains 
of scorpions, spiders, cockroaches and crickets. The Cole- 
optera were also represented, but, as far as we know at 
present, the Lepidoptera did not yet exist; nor is this to be 
wondered at when we consider the entire absence of the 
higher flowering plants. In the waters were numerous fish, 
but the only known air-breathing Vertebrates were Amphibia, 
of which the Labyrinthodonts, huge frog-like animals, were 
the chief. These are known to us principally by the curious 
hand-like footmarks which they left upon the mud. 
The remains of these great sub-tropical forests must have 
formed originally very thick masses of peat, probably ten or 
twenty times thicker than the com! seams they were destined 
to become. This peat consisted, for the most part, of the 
decomposed cellular tissue of plants which grew upon the 
spot; and, within the last few years, we have had a curious 
piece of evidence to show that the initial decomposition of the 
tissue was effected, not bv the mere chemical action of air 
and moisture, but by the agency of those minute living 
organisms which we now recognise as playing such an 
important part in all putrefactive and fermentative change. 
That there are some of you here to-night who are specially 
interested in bacteriology, must be my excuse for referring 
somewhat at length to this interesting fact which, as far as I 
know, has not yet found its way into text-books. 
In the year 1879 Van Tieghem announced to the French 
Academv of Sciences that he had discovered in certain 
microscopic sections of plants from the Coal Measures of 
Saint Etienne, undoubted traces of a minute organism well- 
known to bacteriologists as Bacillus Amylobacter. This 
Bacillus is verv active in the destruction of the cellulose of 
vegetable tissue, and is identical with Pasteur’s butyric acid 
ferment. So we see that in the marshes of the Coal Period 
plants underwent decomposition by identically the same agent 
as they do at the present day, and that even at this very 
remote time, probably separated from our day by millions of 
years, this Bacillus was at work partially destroying the dead 
tissues of the higher plants, and facilitating their conversion 
into coal for our use. This is the onlv well authenticated 
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