The Lepidodendroids and Sigillaroids, 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 existence 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 Conifers_, 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, Paloeoxylon, Araucarioxylon, and Pinites.  Their fruit is not known with absolute certainty, unless it be represented, as often conjectured, by Trigonocarpon (fig. 113).  The fruits known under this name are nut-like, often of considerable size, and commonly three- or six-angled.  They probably originally possessed a fleshy envelope; and if truly referable to the Conifers, they would indicate that these ancient evergreens produced berries instead of cones, and thus resembled the modern Yews rather than 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.

CHAPTER XIII.

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, have been formed in inland swamps and morasses, or in brackish-water lagoons, creeks, or estuaries.  A corresponding difference exists necessarily in the animal remains of these deposits, and in many regions this difference is extremely well marked and striking.  The great marine limestones which characterise the lower portion of the Carboniferous series in Britain, Europe, and the eastern portion of America, and the calcareous beds which are found high up in the Carboniferous in the western States of America, may, and do, often contain the remains of drifted plants; but they are essentially characterised by marine fossils; and, moreover, they can be demonstrated by the microscope to be almost wholly composed of the remains of animals which formerly inhabited the ocean.  On the other hand, the animal remains of the beds accompanying the coal are typically the remains of air-breathing, terrestrial, amphibious, or aerial animals, together with those which inhabit