[Illustration: FIG. 50. _Marchantites Sezannensis_ Sap. _A._ Surface view of the thallus; _g_, ? cups with gemmæ. _B._ A male branch. _C._ A portion of _A_ magnified to show the surface features. (After Saporta.)] The collection of Sézanne fossils in the Sorbonne includes some very beautiful casts of _Marchantites_ in which the structural details are preserved much more perfectly than in the examples described by Saporta. In a few specimens which Prof. Munier-Chalmas recently showed me the reproductive branches were exceedingly well shown. The fossils occur as moulds in the travertine, and the museum specimens are in the form of plaster-casts taken from the natural moulds. Several species of Liverworts belonging to the Marchantiales and Jungermanniales have been recorded from the amber of North Germany, of Oligocene age. These appear to be represented by small fragments, such as are figured by Göppert and Berendt[466] in their monograph on the amber plants, published in 1845. The determinations have since been revised by Gottsche[467], who recognises species of _Frullania_, _Jungermannia_, and other genera. ╭ SPHAGNALES. II. MUSCI. ┤ ANDREAEALES. ╰ BRYALES. The plant-body (gametophyte) in the Musci consists of a stem bearing thin leaves, usually spirally disposed, rarely in two rows. The internal differentiation of the stem is generally well marked, and in some cases is comparable in complexity with the structure of the higher plants. A protonema arises from the spore, having the form of a branched filamentous, or more rarely a thalloid structure. Reproduction as in the group Bryophyta. Mosses like Liverworts have an extremely wide distribution, and occur in various habitats. In many districts vast tracts of country are practically monopolised by peat-forming genera, such as _Sphagnum_ and other Mosses. Some genera are found on rocks at high altitudes in dry regions, a few grow as saprophytes, and many occur either as epiphytes on the leaves and stems of other plants, or carpeting the ground under the shade of forest trees. [Sidenote: DETERMINATION OF MOSSES.]