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.