ASTEROPHYLLITES.
Asterophyllites.—I shall conclude this notice of some of the most characteristic trees of the Carboniferous Flora, with an account of a tribe of plants whose remains are so common in the coal-shales and grits, that there are but few large slabs with vegetable remains that do not exhibit examples of the elegant verticillate foliage of one or more species. The term Asterophyllites, (expressive of the star-like form of the leaves,) applied to this family by M. Ad. Brongniart, includes several fossil plants which are known to geologists under different generic names; the following concise account may be useful to the student.[117]
[117] Consult Tableau des Genres de Végétaux Fossiles, par M. Ad. Brongniart. Diet. d'Hist. Nat. Paris, 1849.
1. Calamodendron.—These are arborescent stems, ligneous internally, and covered with a smooth carbonaceous crust, without regular longitudinal striæ, and not articulated; but the woody axis covered by this bark is deeply striated and articulated, resembling in this respect the true Calamites. These stems have a large central pith, or medullary column, surrounded by a ligneous zone, which is formed of radiated bands, without circles of growth: the structure of the carbonized bark is unknown.
2. Asterophyllites.—These are supposed to be the branches and foliage of the stems above described.
3. Sphenophyllum.—Plants, differing in the form of the leaves, but analogous in structure and mode of fructification to the Asterophyllites.
4. Annularia.—Herbaceous aquatic plants, distinct from the preceding.
5. Volkmannia.—These fossil plants are Asterophyllites in fructification.
The Asterophyllites ([Lign. 42]) had branched articulated stems, with verticillate leaves, arranged perpendicularly to the branches which supported them: but as the foliage is in most instances partially concealed, the natural form is but seldom observable.
The original plants are supposed to have been a tribe of flowering dicotyledons, for small seed-vessels resembling those of the Cypress are often found with the foliage.