FOSSIL COAL PLANTS. 225 
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means of observation, afforded by the excavations, yet such is the magnitude of each 
individual specimen, that we have again to regret the want of additional space to enable 
the examination to be followed up satisfactorily. Fortunately, in one or two instances 
we are enabled to approximate to the probable length of the stems, although in neither 
case are we sure of the exact character of their terminations. Believing that the absence 
of more complete data is an insufficient reason for withholding so much as we really do 
know, I have not scrupled to prepare this memoir. 
One of the instances adverted to, a dichotomous specimen, has a remarkable flexuous 
stem. It would be hazarding too much to guess at its probable length; for both extre- 
mities are concealed. Not less than sixty-five feet, however, in extent, is clearly visible. 
For aught that can be inferred from its present appearance, this tree may have extended 
thirty or forty feet still longer. ‘The other specimen, the most interesting, in fact, of the 
group, shows its lower extremity, near what might have been the root. For the first 
forty feet there is but little diminution or tapering;—perhaps about six inches: so that 
our admeasurements give, in that distance, an average thickness of two feet. Like the 
others with which it is associated, this trunk is flexuous; but is least so towards its 
superior part, for the last forty feet. Seventy feet of this fine stem are exposed within 
the limits of our drawing—we followed it several feet in the coal shale below the level 
surface without discovering any sign cf termination. The specimens exhibited on the 
society’s table were taken from that concealed portion. We may venture to assign a 
height of this tree of from eighty to one hundred feet. During the greatest portion of its 
entire length, a central longitudinal groove or depression appears, somewhat after the 
manner of some Stigmarias and Lepidodendrons. Like the other cases previously 
alluded to, such portions of the carbonized bark as remained on the trunk or mould, 
were extremely thin; readily scaling off, when dry. This bark was not more than from 
z's to sy of an inch in thickness. No traces of any other, or second bark, externally, has 
been observed in any specimen. A third trunk appears near the entrance to the gallery, 
this specimen exhibits more than fifty feet now uncovered, by coal or slate, we might 
judge, from its appearance, that it extended thirty or forty feet farther. 
It is necessary to mention, that none of these trunks were in the extremely compressed 
state, such as is exhibited in those on the bottom slate. They occur as casts, filled with 
indurated clay. When fractured they break in rhomboids, whose acute angle is forty- 
three degrees. Longitudinal flutings are visible throughout the length of these stems, 
and obscure marks of cicatrices, of the smallest class, are of general occurrence. 
There now remains only the important inquiry, under what class and family should 
these magnificent trunks be arranged? In the midst of certain obvious difficulties, we 
have not scrupled to class these dichotomous stems with the Sigillaires, and in that divi- 
sion which is now admitted among the tree ferns. We have even ventured to refer them 
to Segillaires elegans or hexagona. With respect to the Sigillarie which have bifurea- 
tions, M. Brongniart admits that they are confined to a single species, which species 1s 
the Stgillaria elegans. In this he is corroborated by M. Graeser, director of mines, who 
asserts that this character is frequent in that species. : ; 
With regard to the general form of the trunks of Sigillaria, their height, and their 
mode of termination, there is still very incomplete data. We have rarely had occasion 
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