CONCLUDING REMARKS. 45 
botanists and geologists of which our country can boast, one great object 
which I have had in view will be accomplished. In the mean time, how- 
ever, I shall not fail to prosecute the investigation myself. 
_ The subjects that may receive elucidation from a prosecution of this ex- 
amination, are various and important. Thus, if it were determined what 
fossil genera have their stems compressed, and converted entirely into car- 
bonaceous matter, or what species have them hollowed, and filled with sand 
or clay, the cortical part alone remaining, or preserve their internal texture 
more or less entire; or, in the latter case, are filled with siliceous, or with 
calcareous, infiltrations; we should be better enabled to understand the cir- 
cumstances in which these plants existed, or were buried in the strata, as 
well as the mode in which the changes operated upon them have been ef- 
fected. . Some light may also be thrown upon the organization of recent ve- 
getables, by the appearances presented by the fossil species. Thus, the 
double nature of the walls of the cellular tissue, denied by some, appears to 
me established by appearances exhibited by fossil plants. 
It seems somewhat strange, that, notwithstanding the number of works 
in which representations are given of stems, none should have come into my 
hands that present a satisfactory comparative view of the differences of the 
three classes represented in Plate I. ‘This being the case, I may hope that 
the present work will, in so far, be useful to the student of vegetable ana- 
tomy. 
It now only remains for me to assist the geologist who may be desirous 
of viewing these fossil plants for himself, in preparing the objects for the 
microscope. I have the pleasure of laying before my readers a full account 
of the process, for which I am indebted to Mr Nicou. 
Let a thin slice be cut off from the fossil wood, in a direction perpendi- 
cular to the length of its fibres. The slice thus obtained must be ground 
perfectly flat, and then polished. The polished surface is to be cemented 
to a piece of plate or mirror glass, a little larger than itself, and this may be 
-done by means of Canada balsam. <A thin layer of that substance must be 
applied to the polished surface of the slice, and also to one side of the glass. 
