generic characters, yet is evidently nearly allied to the genus, the term ites (from lithos, stone,) is added-as Equisetites, Palmacites, &c. When the fossil plant differs altogether from any known recent genus, it is distinguished by some arbitrary name, as Bucklandia, Stigmaria, &c.

There are also a few provisional genera for the reception of such leaves, fruits, and stems, as are not admissible in the established classification, in consequence of their characters and relations being imperfectly known, as Carpolithes, Endogenites, &c. Upon these principles the following arrangement has been founded: the progess of discovery will, of course, be continually adding to the list, and may probably require the classification to be modified, and some genera to be altogether abandoned.

The arrangement, although commencing with the plants of the most simple structure, the Cellulosæ, and advancing to the higher orders, will not be strictly botanical, for occasionally it will be found convenient to notice species and genera of different orders under the same head, from their occurring under the same geological relations. It is estimated that scarcely one thousand species of plants have been discovered in a fossil state, while the known recent species amount to nearly one hundred thousand.

AGAMIA. The plants of this class have no traces of fructification, and their structure consists of cells alone. It comprises the sea-weeds, and con

fervæ, or fresh-water mosses, as they are commonly termed.

CONFERVITES.-These cellular and aquatic plants are found sometimes in transparent quartz pebbles, and in chalk, in the state of fine ramose filaments, which, by the aid of the microscope, are seen to be articulated. As an example, a beautiful species, discovered by the late Samuel Woodward, Esq., author of the Geology of Norfolk, &c., is here figured.

LIGN. 4.

CONFERVITES WOODWARDII; (G. A. M.)

Chalk, Norfolk.

ALGE. Of this family, which comprises the seaweeds that are not articulated, the Ulvæ and Fuci, many species are found in the mineral kingdom, occurring in the most ancient fossiliferous strata, as well as in the modern deposits. In the Silurian limestone of North America, entire layers of rock

are formed of a large digitate species of fucus (Fucoides Alleghaniensis, Dr. Harlan, Phy. Res.). The Firestone of Bignor in Sussex (Geol. S. E. p. 165.), abounds in a ramose variety, which is figured

in the vignette of the title-page of this volume; it is named Fucoides Targionii (Veg. Foss. p. 56.).

In the chalk flints ramose fuci occasionally occur, but not in a state of preservation that admits of an accurate determination of the forms of the originals. The tertiary marls and limestones of Monte Bolca yield several beautiful species, one of which is here figured in illustration of the genus (Lign. 5.).

LIGN. 6. MOSS AND CONFERVA, in transparent quartz. X 3.

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 occa

sionally imbedded in the pure quartz pebbles called mocha stones, in which they appear with their natural colour, and apparently floating in the transparent medium. A beautiful green moss, with a Conferva twined round its base, is figured Lign. 6. from a specimen of the late Dr. M'Culloch. It appears related to Hypnum (Geol. Trans. Vol. II.).

VASCULAR CRYPTOGAMIA.

The plants of this

class possess, as the name implies, a more complicated structure than the preceding, having vascular tissue as varied as in the flowering or phanerogamous orders.

EQUISETUM. The common species of Equisetum, or Marestail, is a plant that grows in marshy tracts, and on the banks of ditches and rivers; it has a jointed stalk, garnished with elegant sheaths which embrace the stem, and verticillate linear leaves. It grows to the height of two feet, and is half an inch in diameter. In the fossil state there are many plants allied to the Equisetum, but only a few that are generically the same. A species which I discovered in the Ashburnham limestone at Pounceford (Geol. S. E. p. 245.), must have closely resembled the Equisetum fluviatile: it has an articulated stem, and cylindrical, regularly dentated sheaths, embracing the stem at the joints (see Lign. 7.).

A transverse slice of these stems, exhibits under the microscope a cellular structure filled with calc