menophyllacea, and the Marattiacea, go back formation.*

Some of these ferns have the more comp spore-case, with a jointed, elastic ring. It i

a

FIG. 54.-Sphenopteris latior, Dawson. Coal-formation. C magnified, with traces of fructification.

served, however, that those forms which have spore-case, either netted or membranous, and annulus, are most common in the Devonian an

FIG. 55.-Fructification of Paleozoic ferns. a, Theca of A (Erian). b, Theca of Senftenbergia (Carboniferous). c, Asterotheca (Carboniferous).

Carboniferous. Some of the forms in these old r somewhat difficult to place in the system. Of th

* Mr. R. Kidston has recently described very interesting fern fructification from the coal-formation of Great Britain, a has been done by European palæobotanists, and also by Lesque Fontaine in America.

FIG. 56.-Tree-ferns of the Carboniferous. A, Megaphyton magnificum, Dawson, restored. B, Leaf-scar of the same, two thirds natural size. B, Row of leaf-scars, reduced. o, Palæopteris Hartii, scars half natural size. D, Palæopteris Acadica, scars half natural size.

K

species of Archæopteris, of the Upper and M are eminent as examples. This type, howe extends as high as the coal-formation.* tree-ferns of the Carboniferous present very features. One of these, of the genus Megaph to have two rows of great leaves, one at each stem, which was probably sustained by large aërial roots (Fig. 56).

In the Carboniferous, as in the Erian, ther which have been referred to ferns, but are doubt, as possibly belonging to broad-leaved t allied to the gingko-tree of China. One of t

sented in Fig. 57, found in the coal-fo Nova Scotia, and refe doubtful genus No Fontaine has propose lar leaves found in V new generic name Sa Ferns, as might b from their great age, present time dispersed whole world; but th

FIG. 57.-Noeggerathia dispar quarters, and the r

(half natural size).

which tree-ferns are

are the more moist climates of the tropics an southern hemisphere. The coal-swamps of the hemisphere seem to have excelled even these regions of the present world as a paradise for fer

I have already stated that the Carboniferou tutes the headquarters of the Cordaites (Fig. 58), a large number of species have been described,

* The pretty little ferns of the genus Botrychium (moo common in American and European woods, seem to be their ne ern allies.

Europe and America. find their stems showing structure. In this case we have a large cellular pith, often divided by horizontal partitions into flat chambers, and constituting the objects which, when detached, are called Sternbergia (Fig. 62). These Sternbergia piths, however, occur in true conifers as well, as they do

We sometimes, though rarely,

in the modern world in some trees, like our common butternut, of higher type; and I showed many years ago that the Sternbergia type may be detected in the young twigs of the balsam-fir (Abies balsamifera). The pith was surrounded by a ring of scalariform or barred tissue, often of considerable thickness, and in young stems so important as to have suggested lycopodiaceous affinities. But as the stem grew in size, a regular ring of woody wedges, with tissue having rounded or hexagonal pores or discs, like those of pines, was developed. Outside this was a bark, often apparently of some thickness. This structure in many important points resembles that of cycads, and also approaches to the structure of Sigillaria, while in its more highly developed forms it approximates to that of the conifers.

On the stems so constructed were place often broad many-nerved leaves, with rows of breathing-pores, and attached by somewhat to the stem and branches. The fruit consisted or clusters of nutlets, which seem to have bee

FIG. 59.-Fruits of Cordaites and Taxine Conifers (coal-forma Scotia.) A, Antholithes squamosus (two thirds). B, A. r (two thirds). B1, Carpel restored. A. spinosus (nat D, Trigonocarpum intermedium. E, Noggerathii. F, пит. o, Rhabdocarpus insignis, reduced. H, Antholithes 1, Cardiocarpum fluitans. K, Cardiocarpum bisectum. L, S papillata, lycopodiaceous macrospores (natural size and mag