the flattened bark of Sigillarioid and other trees, intermixed
with leaves of Ferns and _Cordaites_, and other herbaceous
_débris_, and with fragments of decayed wood, constituting
'mineral charcoal,' all these materials having manifestly
alike grown and accumulated where we find them."[1]

[Footnote 1: "Acadian Geology," 2nd edition, p. 138.]

When I had the pleasure of seeing Principal Dawson in London last
summer, I showed him my sections of coal, and begged him to re-examine
some of the American coals on his return to Canada, with an eye to the
presence of spores and sporangia, such as I was able to show him in
our English and Scotch coals. He has been good enough to do so; and in
a letter dated September 26th, 1870, he informs me that--

"Indications of spore-cases are rare, except in certain coarse
shaly coals and portions of coals, and in the roofs of the
seams. The most marked case I have yet met with is the shaly
coal referred to as containing _Sporangites_ in my paper
on the conditions of accumulation of coal (_Journal of the
Geological Society_, vol. xxii. pp. 115, 139, and 165). The
purer coals certainly consist principally of cubical tissues
with some true woody matter, and the spore-cases, &c.,
are chiefly in the coarse and shaly layers. This is my old
doctrine in my two papers in the _Journal of the Geological
Society_, and I see nothing to modify it. Your observations,
however, make it probable that the frequent _clear spots_ in
the cannels are spore-cases."

Dr. Dawson's results are the more remarkable, as the numerous