These considerations serve, I think, to explain all the apparently anomalous associations of coal plants with marine fossils; and I do not know any other arguments of apparent weight that can be adduced in favour of the marine or even aquatic origin of coal, except such as are based on misconceptions of the structure and mode of growth of sigillaroid trees and of the stratigraphical relations of the coal itself.[145] It is to be observed, however, that while I must maintain the essentially terrestrial character of the ordinary coal and of its plants, I have elsewhere admitted that cannel coals and earthy bitumen present evidences of subaquatic deposition; and have also abundantly illustrated the facts that the coal plants grew on swampy flats, liable not only to river inundations, but also to subsidence and submergence.[146] In the oscillation of these conditions it is evident that _Sigillariæ_ and their contemporaries must often have been placed in conditions unfavourable or fatal to them, and when their remains are preserved to us in these conditions, we may form very incorrect inferences as to their mode of life. Further, it is to be observed that the conditions of submergence and silting up which were favourable to the preservation of specimens of _Sigillariæ_ as fossils, must have been precisely those which were destructive to them as living plants; and on the contrary, that the conditions in which these forests may have flourished for centuries must have been those in which there was little chance of their remains being preserved to us, in any other condition at least than that of coal, which reveals only to careful microscopic examination the circumstances, whether aërial or aquatic, under which it was formed.