The roots of these trees were equally remarkable with their stems, and so dissimilar to any now existing that botanists were long disposed to regard them as independent plants rather than roots. They were similar in general structure to the stems to which they belonged, but are remarkable for branching in a very regular manner by bifurcation like the stems above, and for the fact that their long, cylindrical rootlets were arranged in a spiral manner and distinctly articulated to the root after the manner of leaves rather than of rootlets, and fitting them for growing in homogeneous mud or vegetable muck. They are the so-called _Stigmaria_ roots, which, though found in the Erian and belonging to its lycopodiaceous plants, attained to far greater importance in the Carboniferous period, where we shall meet with them again. There were different types of lycopodiaceous plants in the Erian. In addition to humble Lycopods like those of our modern woods and great Lepidodendra, which were exaggerated Lycopods, there were thick-stemmed and less graceful species with broad rhombic scars (_Leptophleum_), and others with the leaf-scars in vertical rows (_Sigillaria_), and others, again, with rounded leaf-scars, looking like the marks on Stigmaria, and belonging to the genus _Cyclostigma_. Thus some variety was given to the arboreal club-mosses of these early forests. (See Fig. 15.) [Illustration: Fig. 22.--Erian ferns (New Brunswick), A, _Aneimites obtusa_. C, _Neuropteris polymorpha_. F, _Sphenopteris pilosa_. N, _Hymenophyllites subfurcatus_.] Another group of plants which attained to great development in the Erian age is that of the Ferns or Brackens. The oldest of these yet known are found in the Middle Erian. The _Eopteris_ of Saporta, from the Silurian, at one time supposed to carry this type much further back, has unfortunately been found to be a mere imitative form, consisting of films of pyrites of leaf-like shapes, and produced by crystallisation. In the Middle Erian, however, more especially in North America, many species have been found (Figs. 22 to 24).[AW] I have myself recorded more than thirty species from the Middle Erian of Canada, and these belong to several of the genera found in the Carboniferous, though some are peculiar to the Erian. Of the latter, the best known are perhaps those of the genus _Archæopteris_ (Fig. 24), so abundant in the plant-beds of Kiltorcan in Ireland, as well as in North America. In this genus the fronds are large and luxuriant, with broad obovate pinnules decurrent, on the leaf-stalk, and with simple sac-like spore-cases borne on modified pinnæ. Another very beautiful fern found with _Archæopteris_ is that which I have named _Platyphyllum_, and which grew on a creeping stem or parasitically on stems of other plants, and had marginal fructification.[AX] Another very remarkable fern, which some botanists have supposed may belong to a higher group than the ferns, is Megalopteris (Fig. 26).