178 
Transactions of the 
rMonthly Microscopical 
L Journal, Oct. 1, 1869. 
shale formed the soil on which grew extensive cryptogamic forests, 
that were snccessively destroyed when in their prime hy showers of 
volcanic ash, which broke down and buried in its mass the branches, 
and left as bare poles the scorched and dead stems rising high 
above the ash as witnesses of the terrible destruction. In the 
course of time they were hidden by the gro\N'th of a luxmiant vege- 
tation which speedily covered the new soil, but only to be destroyed 
by a fresh outburst from the intermittently active volcano in their 
neighbourhood. Frequently spores found a suitable nidus in the 
decayed and hollow interior of these immense stems. Mr. Wunsch 
has given me specimens, in which from six to nine young trees, 
with stems from two to three inches in diameter, belonging pro- 
bably to several distinct species and at least to two genera, have 
grown by the side of each other within a single trunk. The frag- 
ments of the branches in the beds of tufa retain to a great extent 
their original form, and the minute structure is often preserved in 
a singularly perfect manner. In addition to the specimens I myself 
collected, I have been supplied in the most liberal manner by 
Mr. Wunsch with specimens collected by himself. I am also 
indebted to Mr. J. Young, of the Hunterian Museum, Glasgow, 
for some interesting specimens he obtained from the same locality. 
Professor Morris has supplied me with several important speci- 
mens from the Lancashire coal-field. The grant placed at my 
disposal by the British Association has enabled me to have these 
various materials prepared by the lapidary, so as to be able to 
make the most exact microscopical examination of their structure. 
In addition to these, I have had the use of several fine preparations 
from the cabinet of Dr. J. Millar ; I have examined the valuable 
series of microscopic preparations recently acquired by the British 
Museum, made by Nicol (the inventor of the method of slicing 
fossils) and Bryson, and the yet more valuable collection made by 
Kobert Brown, and bequeathed by him to the same institution. 
The specimens exhibiting structure are generally in nodules in 
the coal. The conditions which were favourable to the accumula- 
tion and preservation of the plant-remains of the Coal period in a 
state of purity that makes them now invaluable to man, did not 
also favour the conservation of those characters which would enable 
us to determine the nature of the plants themselves. With the 
exception of the thin layers of charcoal, commonly called " Mother- 
coal," the origin of which has never been satisfactorily accounted 
for, the whole mass of vegetable matter was speedily reduced to a 
homogeneous and amorphous condition by decay, greatly assisted 
by the abundant water. The covering of plastic clay, now indu- 
rated into the shale, which invariably forms the "roof" of every 
good seam of coal, stopped the progress of decomposition, and 
sealed up the precious deposit against the intrusion of injurious 
substances like iron or lime. It is only where this cover has been 
