Of the little plants comprised in the class of cellular cryptogamia, which have stems, leaves, and fructification, but no true vessels, two or three species of Moss and Liverwort have been met with in tertiary strata. Mosses as well as Fuci are occasionally imbedded in quartz pebbles, in which they appear of their natural colour, and apparently floating in the transparent medium. A beautiful green moss, with a Conferva twined round its base, is figured _Lign. 11_ , p. 104, from a specimen described by the late Dr. Macculloch. It is supposed to be related to _Hypnum_ (_Geol. Trans._ vol. ii.). [Sidenote: MOCHA-STONES.] Moss-agates and Mocha-stones.--The beautiful siliceous pebbles called Moss-agates, and Mocha-stones, will so often come under the notice of the collector, that, although but extremely few, if any, of these objects contain organic remains, the arborescent substances they inclose being merely metallic oxides, a few remarks on their nature may be expected. The late Dr. Macculloch paid considerable attention to the investigation of these bodies, and believed that some of the objects imbedded in the pure and compact quartz were really of vegetable or animal origin; the specimen figured _Lign. 11_ is of this kind; the fossils being apparently cellular cryptogamous plants. In _Geol. Trans_, vol. ii., other examples are figured and described by the same sagacious observer. Mr. Bowerbank is of opinion that spongeous structure enters into the composition of almost all the moss-agates, and I have no doubt that in some instances such organisms are present: but in by far the greater number of agates and mocha-stones the inclosed bodies are mere crystallizations; they are arborescent or dendritical oxides of manganese, copper, chlorite, iron, &c. [Illustration: Lign. 10 Delesserites (Fucoides) Lamourouxii. _Monte Bolca._ (_Vég. Foss. Br._)] [Illustration: Lign. 11. Moss and Conferva, in transparent quartz, × 3.] M. Brongniart, who carefully examined a great number of agates and pebbles, with the view of determining if vegetable substances were ever imbedded in them, could not detect a single instance in which the apparent mosses, confervæ, or algæ, were organic; in every case the mineral origin of the pseudo-vegetation was, in his opinion, unequivocal. Some of the beautiful green arborescent bodies in quartz pebbles, even under the microscope, present so close a resemblance to confervæ and mosses, that it is difficult to persuade oneself they are not vegetable structures; but the observations of M. Brongniart appear to me conclusive as to their mineral nature.[75] With the exception of three or four species of _Jungermannia_, and four or five of _Muscites_ in Amber, M. Brongniart states that he knows but one true fossil plant of the family of Mosses; the _Muscites Tournalii_ from the fresh-water tertiary deposits of Armissan. [75] See Histoire des Végétaux Fossiles, pp. 29-34.