368 On the Vegetation of the Carboniferous Period^ 



must not seek to force a plant into a natural order, the habits of 

 whose existing species are incompatible with those conditions under 

 which a more comprehensive view of the coal formation may assure 

 him it must have vegetated ; nor can the geologist put forward any 

 theory which will explain the features of that formation, if it be 

 grounded on views opposed to those few certain data, which a study 

 of the botany of the period in question has afforded. 



There is another branch of this investigation of equal importance 

 to the geologist and botanist, namely, the identification and compa- 

 rison of the species from different and sometimes remote coal-fields, 

 or from the various strata of the same field. This is as difficult as 

 any of the points which occupy the botanist ; and all questions con- 

 nected with the geographical distribution of the plants of that pe- 

 riod being dependent on the results thus obtained, it is one which 

 requires extreme caution in the working. The obvious tendency in 

 the student is to regard as identical the similar fossils in the various 

 strata exposed in one mine, and as different the plants from remote 

 coal-fields. From recent observations, it appears that subsequent 

 movements may have isolated portions of what once formed a conti- 

 nuous bed of coal, characterised by a uniform vegetation throughout, 

 and that hence a slight dissimilarity between the plants of each por- 

 tion may be attributable to a difference in the conditions to which it 

 was exposed in each. On the other hand, it must be borne in mind, 

 that at the present day a change in position is almost surely accom- 

 panied by a very considerable change in vegetation. The labour of 

 identification, too, is not confined to the comparison of specimens, 

 but includes the determination of their names when previously de- 

 scribed. This is often all but impossible, from the nature of the 

 specimens, and the difficulty of presenting them, in an available form, 

 without plates. Hence it happens that the labour of individual ob- 

 servers is overlooked. It is, perhaps, impossible to employ similar 

 materials to better purpose than has the author of the " Flore Fos- 

 sile" those upon which he laboured; and yet the difficulty of naming 

 the species by that work is very great, and must be so ; for the spe- 

 cimens to be compared are, like originals, mere fragments, and the 

 genera of Ferns adopted are far from being properly defined, though 

 as judiciously as the materials would permit. On the contrary, 

 many of these are not supported by the examination of living ana- 

 logues; whilst others are unavoidably founded on isolated portions of 

 plants, whose appeai*ances, whilst living, and affinities are alike un- 

 known, whether amongst their contemporaries by which the world 



to the order Eupliorhiacece , by others to Cacti, and by the majority to Ferna. 

 The necessary conclusion to which those who place them in the first two orders 

 would lead us is, that they were inhabitants of singularly aiid and desert coun- 

 tries; whilst, if ferns, they are characteristic of diametrically opposite condi- 

 tions, — a moist soil and a humid atmosphere. 



