CONTAINED IN NODULES OF LIMESTONE. 
155 
The abundance of these Trigonocarpons in the nodules, and the fact of their 
lying at all angles and in all positions, suggests the probability of their having fallen 
from a height into a soft or spongy mass of decaying vegetable matter ; and it may 
be noticed, that the very similar fruits of Podocarpus ferruginea, a New Zealand 
drupe-bearing Conifer, are in like manner shed in profusion from the lofty trees 
that produce them, and become imbedded in the swamps out of which the trees 
grow ; and that the latter are often covered with Ferns and Lycopodia in great pro- 
fusion, the decay of all which produces a spongy bog, in consistence not unlike that 
of the mass in which the Trigonocarpons are imbedded. Such comparisons cannot, 
however, be carried far ; for whereas these New Zealand bogs, and the clay upon 
which they almost invariably rest, are everywhere traversed by woody roots of coni- 
ferous trees, we find in the substance of the limestone nodules and in the underclay 
of the coal no trace of these, but in the latter SigUlaria roots abundantly (viz. Stig~ 
maria Jicoides). In our present state of knowledge (or rather ignorance) of the phy- 
siognomy, as well as of the botanical characters of the vegetation of the coal epoch, 
all references of detached organs are extremely rash, and in the present case we 
cannot venture beyond alluding to the facts, that the flower and fruit of SigUlaria 
are totally unknown, and that these and Trigonocarpon fruit and Noggerathia leaves 
are very abundant throughout the coal formation. There is another curious point, 
to which also we can only incidentally allude, which is, that Salisburia has several 
embryos in each seed-, which in germinating become as many young plants : these 
often coalesce at a very early period, and the result is a compound tree, with one 
main axis, but as many primary roots as there were embryos : though ofiering no 
explanation of the phenomenon, it may be mentioned as a curious circumstance, 
that the base of every SigUlaria trunk is marked by a cruciform ridge, separating 
the four primary divisions of the root, of which ridge no explanation has ever been 
offered. 
With regard to the evidence of Coniferae having existed during the carboniferous 
period, we are far from considering that afforded by the wood abounding in discs as 
conclusive, however much these resemble the discs of Araucaria : it is now well 
known that very similar discs abound in the wood of many Natural Orders that have 
no alliance with Coniferce ; but it is not hitherto known that there is a coniferous tree, 
in which the discs are not present in all parts of the wood, but are totally absent from 
one-half of each annual wood deposit. This tree, probably a drifted one, was dis- 
covered on the shores of Wellington Channel by Sir Edward Belcher, and it renders 
it not impossible that coniferous wood may be found in which these discs are totally 
absent. It is now, however, universally admitted by those botanists who have made 
both the anatomieal structure and affinities of plants their study, that the structure of 
the axis of Exogens affords no guide to their affinity ; Coniferce have been supposed to 
form the best marked exception to this rule, and there is no doubt that they do so ; 
but the coniferous woods of the coal epoch present so many remarkable deviations 
