42 CONCLUDING REMARKS. 
decidedly observable in the Coniferee of the lias; as in Figs. 3, and 4, of 
the lower part of Plate IV., and in Figs. 1, 2, and 3, of Plate V. There- 
fore, at the epoch when the trees of the lias grew, there was a cold season as 
now. 
Between the monocotyledonous fossil and recent species which I have 
figured, no comparison can be instituted, as they are not of the same spe- 
cies; but it may be remarked generally, that, so far as I have examined 
these plants, the recent species have smaller cells and vessels than the fos- 
sil. 
The same remark is to be made of the dicotyledonous woods, 
Of the recent Coniferz, figured in Plate I., Figs. 1, 2, 3, and 4, are of 
climates similar to that in which the fossil Conifere figured in Plates IT, 
III, IV, V, and VI. occur. Still, even here, no accurate comparison can 
be instituted, as we cannot decide upon the genera, much less upon the spe- 
cies, of the fossil plants. But it may be generally remarked, that the cells 
or tubes of the latter are, in almost every case, much larger than those of 
the former. Thus, Figs. 1, 2, 3, 4, 5, 6, '7, and 8, of Plate IV., which are 
enlarged in the same degree as Figs. 1, 2, 3, and 4, of Plate I., have much 
larger meshes than the latter; while Fig, 3. of the lower part of Plate IV. 
has its meshes as large as those of the recent Conifer in Plate I., although 
enlarged in a much less degree. 
Our observations on this subject, however, are not sufficiently numerous 
or correct, to authorize any inferences as to the comparative vigour of the 
vegetation of the different epochs, although they are sufficient, along with 
other circumstances, to render it not improbable that the temperature was 
higher at the periods when the fossil vegetables grew than it is now. 
The general colour of the fossil vegetables, retaining their organic texture, 
which occur in our mountain limestone groups, coal-fields, and lias deposits, 
is brown, of various tints, more commonly wood-brown, frequently umber, 
and sometimes greyish or blackish-brown. These fossils are all more or less 
calcareous, and the veins by which they are frequently intersected, are ge- 
nerally of calcareous spar. Those fossils, on the contrary, which, occurring 
in the same formations, are destitute of organic texture, have their interior 
