FUCOIDES IN THE COAL FORMATIONS. 



323 



ceding periods the sea brings with it and disseminates the seeds and branches of its Hy- 

 drophitcs, which germinate again, reproducing identical forms wherever circumstances are 

 favorable to their development. But that terrestrial plants, like those of which the coal is 

 a compound, should have been exposed to some modification of life after each of those 

 revolutions, which so often totally changed the surface of the land during the Car- 

 boniferous epoch, is an assertion which can only be considered reasonable. For each of 

 these revolutions may have influenced the atmosphere, either in its degree of density or 

 of humidity, or in its chemical compounds. Moreover, each of them at least has evidently 

 modified the land-stations inhabited by the plants, either by leaving the surface more or 

 less penetrated with humidity, or by covering it with deposits of another nature, or with 

 other elements of vegetation, sand, lime, mud, &c. 



This assertion does not force us to the conclusion that all the plants of the Coal Measures 

 have been totally destroyed after each submersion of the land, and been replaced by other 

 species ; but only that some of the predominant species have lost in the number of their 

 representatives; that a few have disappeared, while new kinds have taken their place; 

 and that accordingly, for any particular horizon, the group of vegetation has a character 

 which may be recognized in its fossil remains, and serve as a true and reliable guide for 

 the identification of the coal strata. 



This is not said as a reaffirmation of a personal opinion expressed elsewhere.* For, with 

 a few exceptions, all the authors who have studied the fossil plants of the coal, in relation 

 to their habitat, have come to the same conclusion. Prof. Brongniart's remarks on this 

 subject are worth recording. He says :f "But if the vegetation of our earth has been main- 

 tained without great changes during this whole period of time (the Carboniferous epoch), 

 it is not the less certain that very marked changes in the species may be observed during 

 the deposition of the various strata. Thus, in one and the same coal basin, each bed has 

 characteristic species which are not found in more ancient or more recent strata, and which 

 the miners themselves recognize as peculiar to a coal bed." Another celebrated European 

 palaeontologist and botanist, Prof. W. P. Schimper, of Strasbourg, records the same fact 

 in a recent work, saying^: that in the same coal basin a variation of species is observable 

 in passing from the inferior to tlve superior strata. So remarkable is this change that the; 

 highest strata of the true Coal Measures are marked already by species which, like 

 Pterophyllum, are characteristic of the Trias, or even of the lower Jurassic formations. 



Though the researches on the paloeontological botany of our American coal fields are 

 only in an incipient state, and thus our acquaintance with the leading species of various 



* American Journal of Sciences and Arts (2), vol. 80, p. 367, Geological Reports, &c. 



j- Tableau des Genres (1849), p. 95. 



X Terrains de Transition des Vosges, Partie Palteontologique (1862), p. 318. 



