170 HISTORICAL PALAZZONTOLOGY. 
the “ under-clay,” which forms the floor of a bed of coal, and 
which represents the ancient soil upon which the Szgz//ar@ grew. 
The Lepidodendroids and Sigillarioids, though the first were 
certainly, and the second possibly, Cryptogamic or flowerless 
plants, must have constituted the main mass of the forests of 
the Coal period; but we are not without evidence of the exist- 
ence at the same time of genuine “trees,” in the technical 
sense of this term—namely, flowering plants with large woody 
stems. So far as is certainly known, all the true trees of the 
Carboniferous formation were Covdfers, allied to the existing 
Pines and Firs. They are recognised by the great size and 
concentric woody rings of their prostrate, rarely erect trunks, 
and by the presence of disc-bearing fibres in their wood, as 
demonstrated by the microscope; and the principal genera 
which have been recognised are Dadoxylon, Paleoxylon, 
Araucarioxylon, and Pinites. Their fruitis not known with 
absolute certainty, unless it be represented, as often conjectured, 
by Z7rigonocarpon (fig. 113). The fruits known under this 
name are nut-like, often of consider- 
able size, and commonly three- or six- 
angled. They probably originally pos- 
sessed a fleshy envelope; and if truly 
referable to the Conzfers, they would 
indicate that these ancient evergreens 
: produced berries instead of cones, 
Fig. 113. — Trigonocarfon and thus resembled the modern Yews 
ovatunz, Coal-measureg, Britain. : 
(adver Lindley cect Peatean) rather than the Pines. It seems, 
further, that the great group of the 
Cycads, which are nearly allied to the Conifers, and which 
attained such a striking prominence in the Secondary period, 
probably commenced its existence during the Coal period ; 
but these anticipatory forms are comparatively few in number, 
and for the most part of somewhat dubious affinities. 
CEA PTER. axis 
THE CARBONIFEROUS PERIOD—Continued. 
ANIMAL LIFE OF THE CARBONIFEROUS. 
We have seen that there exists a great difference as to the 
mode of origin of the Carboniferous sediments, some being 
purely marine, whilst others are terrestrial; and others, again, 
