menophyllaceæ, and the Marattiaceæ, go back to the coalformation.*

Some of these ferns have the more complex kind of spore-case, with a jointed, elastic ring. It is to be ob

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

served, however, that those forms which have a simple spore-case, either netted or membranous, and without annulus, are most common in the Devonian and lowest

FIG. 55. Fructification of Palæozoic ferns. a, Thecæ of Archæopteris (Erian). b, Theca of Senftenbergia (Carboniferous). c, Thecæ of Asterotheca (Carboniferous).

Carboniferous. Some of the forms in these old rocks are somewhat difficult to place in the system. Of these, the

* Mr. R. Kidston has recently described very interesting forms of fern fructification from the coal-formation of Great Britain, and much has been done by European palæobotanists, and also by Lesquereux and 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. B1, Row of leaf-scars, reduced. c, Palæopteris Hartii, scars half natural size. D, Palæopteris Acadica, scars half natural size.

K

species of Archæopteris, of the Upper and м are eminent as examples. This type, howe extends as high as the coal-formation.* ន tree-ferns of the Carboniferous present very features. One of these, of the genus Megapl 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 re

(half 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 (moc common in American and European woods, seem to be their ne ern allies.

Europe and America. We sometimes, though rarely, 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 Sternbergiæ (Fig. 62). These Sternbergia piths, however, occur in true conifers as well, as they do 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 placed long and often broad many-nerved leaves, with rows of stomata or breathing-pores, and attached by somewhat broad bases to the stem and branches. The fruit consisted of racemes, or clusters of nutlets, which seem to have been provided

FIG. 59. Fruits of Cordaites and Taxine Conifers (coal-formation, Nova Scotia.) A, Antholithes squamosus (two thirds). в, A. rhabdocarpi (two wo thirds). B1, Carpel restored. c, A. spinosus (natural size). D, Trigonocarpum intermedium. E, T. Naggerathii. F, T. avellaG, Rhabdocarpus insignis, reduced. H, Antholithes pygmæus. 1, Cardiocarpum fluitans. K, Cardiocarpum bisectum. L, Sporangites papillata, lycopodiaceous macrospores (natural size and magnified).