. Elements of geology : a text-book for colleges and for the general reader. Geology. LIFE-SYSTEM OF DEVONIAN AGEâPLANTS. 329 The Ferns were represented by several genera, such as Cyclopteris and Neuropteris; the Lycopods (club-mosses) not only by the Psilophy- ton, which had been already introduced in the uppermost Silurian, but also now by gigantic L&pidodendrids and Sigillarids, and the Equi- setae by Calamites and Asterophyllites. The Conifers were represented by the genus Protaxites, allied to the yew (Taxus). They are known to be conifers by their concentric rings of growth and gymno
. Elements of geology : a text-book for colleges and for the general reader. Geology. LIFE-SYSTEM OF DEVONIAN AGEâPLANTS. 329 The Ferns were represented by several genera, such as Cyclopteris and Neuropteris; the Lycopods (club-mosses) not only by the Psilophy- ton, which had been already introduced in the uppermost Silurian, but also now by gigantic L&pidodendrids and Sigillarids, and the Equi- setae by Calamites and Asterophyllites. The Conifers were represented by the genus Protaxites, allied to the yew (Taxus). They are known to be conifers by their concentric rings of growth and gymnospermous tissue, i. e., the elliptic disk-like markings on the walls of the wood- cells on longitudinal section (Figs. 389 and 390), and the entire absence on cross-section of the visible pores so character- istic of dycolytedonous Exogens (Fig. 391). Some of these conifers have been found by Daw- son eighteen inches, and one three feet, in diam- eter. There have been fifty species of land- plants of these various orders found by Daw- fig. 391.âPine-wood, cross- ,-â r, ⢠4? at ci x- i t Section magnified. son m the Devonian 01 JNova Scotia alone. In Figs. 392-402 we give the most characteristic Devonian land-plants. General Remarks on Devonian Land-Plants.âWe will not at present discuss the affinities of these plants, and their relations to evolution, because they are similar to those found in the coal, where they exist in far greater variety and abundance, and the subject will be discussed under that head. There are, however, some thoughts suggested by the first appearance of highly-organized plants which ought not to be omitted: 1. The ringed structure of Devonian conifers shows that, at that time, there was a growing season and a season of rest, and therefore, probably, a warm and a cold season. In one trunk the number of rings counted was 150, indicating a considerable age. 2. "What were the precursors of this highly-organized forest vegeta- tion? That there ive
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