The second specimen of this species represents a lower part of the stem. It is thirteen inches long and about four inches in diameter, and is covered with a mass of flattened aërial roots lying parallel to each other, in the manner of the Psaronites of the coal-formation and of P. Erianus of the Upper Erian or Devonian.
4. Asteropteris noveboracensis, gen. and sp. n.—The genus Asteropteris is established for stems of ferns having the axial portion composed of vertical radiating plates of scalariform tissue embedded in parenchyma, and having the outer cylinder composed of elongated cells traversed by leaf-bundles of the type of those of Zygopteris.
The only species known to me is represented by a stem 2·5 centimetres in diameter, slightly wrinkled and pitted externally, perhaps by traces of aërial roots which have perished. The transverse section shows in the centre four vertical plates of scalariform or imperfectly reticulated tissue, placed at right angles to each other, and united in the middle of the stem. At a short distance from the centre, each of these plates divides into two or three, so as to form an axis of from ten to twelve radiating plates, with remains of cellular tissue filling the angular interspaces. The greatest diameter of this axis is about 1·5 centimetre. Exterior to the axis the stem consists of elongated cells, with somewhat thick walls, and more dense toward the circumference. The walls of these cells present a curious reticulated appearance, apparently caused by the cracking of the ligneous lining in consequence of contraction in the process of carbonization. Embedded in this outer cylinder are about twelve vascular bundles, each with a dumb-bell-shaped group of scalariform vessels enclosed in a sheath of thick-walled fibres. Each bundle is opposite to one of the rays of the central axis. The specimen shows about two inches of the length of the stem, and is somewhat bent, apparently by pressure, at one end.
This stem is evidently that of a small tree-fern of a type, so far as known to me, not before described,[BK] and constituting a very complex and symmetrical form of the group of Palæozoic ferns allied to the genus Zygopteris of Schimper. The central axis alone has a curious resemblance to the peculiar stem described by Unger (“Devonian Flora of Thuringia”) under the name of Cladoxylon mirabile; and it is just possible that this latter stem may be the axis of some allied plant. The large aërial roots of some modern tree-ferns of the genus Angiopteris have, however, an analogous radiating structure.
[BK] Prof. Williamson, to whom I have sent a tracing of the structure, agrees with me that it is new.
The specimen is from the collection of Berlin H. Wright, Esq., of Penn Yan, New York, and was found in the Portage group (Upper Erian) of Milo, New York, where it was associated with large petioles of ferns and trunks of Lepidodendra, probably L. Chemungense and L. primævum.
The occurrence of this and other stems of tree-ferns in marine beds has recently been illustrated by the observation of Prof. A. Agassiz that considerable quantities of vegetable matter can be dredged from great depths in the sea on the leeward side of the Caribbean Islands. The occurrence of these trunks further connects itself with the great abundance of large petioles (Rhachiopteris) in the same beds, while the rarity of well-preserved fronds is explained by the coarseness of the beds, and also by the probably long maceration of the plant-remains in the sea-water.
In connection with this I may refer to the remarkable facts recently stated by Williamson[BL] respecting the stems known as Heterangium and Lyginodendron. It would seem that these, while having strong exogenous peculiarities, are really stems of tree-ferns, thus placing this family in the same position of advancement with the Lycopods and Equisetaceæ of the Coal period.
[BL] “Proceedings of the Royal Society,” January 6, 1887.
IV.—On Erian Trees of the Genus Dadoxylon, Unger.
(Araucarites of Goeppert, Araucarioxylon of Kraus.)