FIG. 23. Erian ferns (New Brunswick). B, Cyclopteris valida, and pinnule enlarged. D, Sphenopteris marginata, and portion enlarged. E, Sphenopteris Sphenopteris Hartii. G, Hymenophyllites curtilobus. H, Hymeпоphyllites Gersdorffii, and portion enlarged. enlarged. I, Alethopteris discrepans. K, Pecopteris serrulata. Pecopteris 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.*

a

FIG. 24. Archæopteris 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 series of stays like the cordage of a ship. This method of support

FIG. 26. Megalopteris Dawsoni, Hartt (Erian, New Brunswick). a, Fragment of pinna. 6, Point of pinnule. c, Venation. (The midrib is not accurately given in this figure.)

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

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 Falkenberg, in Germany, and of Saalfeld, in Thuringia, by Goeppert and Unger, and are referred to ferns by the former, but treated as doubtful

This

by the latter.
peculiar type of tree-
fern is apparently a
precursor of the more
exogenous type of
Heterangium, recent-
ly described and re-
ferred to ferns by
Williamson. Here,
again, we have a me-
chanical contrivance
now restricted to
higher plants appro-
priated by these old
cryptogams.

FIG. 27.-Calamites radiatus (Erian, New
Brunswick).

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."