FIG. 23.-Erian ferns (New Brunswick). B, Cyclopteris valida, and pinnule enlarged. D, Sphenopteris marginata, and portion enlarged. E, Sphenopteris Hartii. &, Hymenophyllites curtilobus. H, Hymenophyllites Gersdorffii, and portion enlarged. 1, Alethopteris discrepans. K, Pecopteris serrulata. L, Pecopteris preciosa. M, Alethopteris Perleyi.

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.*

FIG. 24.-Archeopteris Jacksoni, Dawson (Maine). An Upper Erian fern. a, b, Pinnules showing venation.

"Reports on Fossil Plants of the Devonian and Upper Silurian of

Canada," 1871, &c.

Another very remarkable fern, which some botanists have supposed may belong to a higher group than the ferns, is Megalopteris (Fig. 26).

Some of the Erian ferns attained to the dimensions of tree-ferns. Large stems of these, which must have floated out far from land, have been found by Newberry in the marine limestone of Ohio (Caulopteris antiqua and C. peregrina, Newberry),* and Prof. Hall has found in the

FIG. 25.-An Erian tree-fern. Caulopteris Lockwoodi, Dawson,
reduced. (From a specimen from Gilboa, New York.)

Upper Devonian of Gilboa, New York, the remains of a forest of tree-ferns standing in situ with their great masses of aërial roots attached to the soil in which they grew (Caulopteris Lockwoodi, Dn.).†

These aërial roots introduce us to a new contrivance for strengthening the stems of plants by sending out into the soil multitudes of cord-like cylindrical roots from

* "Journal of the Geological Society," 1871.

+ Ibid.

various heights on the stem, and which form a stays like the cordage of a ship. This method o

FIG. 26.-Megalopteris Dawsoni, Hartt (Erian, New Brunswick), a ment of pinna. b, Point of pinnule. c, Venation. (The midril accurately given in this figure.)

still continues in the modern tree-ferns of the tr and the southern hemisphere. In one kind of tree

stem from the Erian of New York, there is also a special arrangement for support, consisting of a series of peculiarly arranged radiating plates of scalariform vessels, not exactly like those of an exogenous stem, but doing duty for it (Asteropteris).*

Similar plants have
been described from
the Erian of Falken-
berg, in Germany,
and of Saalfeld, in
Thuringia, by Goep-
pert and Unger, and
are referred to ferns
by the former, but
treated as doubtful
by the latter.
peculiar type of tree-

This

fern is apparently a precursor of the more exogenous type of Heterangium, recently described and referred to ferns by Williamson. Here, again, we have a mechanical contrivance now restricted to higher plants appropriated by these old cryptogams.

The history of the ferns in geological time is remarkably different from that of the Lycopods; for while the

* "Journal of the Geological Society," London, 1881.

+"Sphenopteris Refracta," Goeppert; "Flora des Uebergangsgebirges." "Cladoxylon Mirabile," Unger; "Palæontologie des Thuringer Waldes."