STUDIES OF PALEOZOIC FERNS. THE MORPHOLOGY, ANATOMY, AND TAXONOMY OF ANKYROPTERIS GLABRA

EGGERT, DONALD A. (Yale U., New Haven, Conn.) Studies of Paleozoic ferns. The morphology, anatomy, and taxonomy of Ankyropteris glabra. Amer. Jour. Bot. 46(7): 510-520. Illus. 1959.-This is a morphological and taxonomic study of the American specimens of Ankyropteris, with the exception of A. hendricksi, that previous to this time have been referred to A4. grayi, originally a Lower Carboniferous species from England, and to A. glabra, a MiddlePennsylvanian form from Booneville, Indiana. The problem of the separation of these two closely allied species is discussed, and the original criteria for separation are questioned, on the basis of four specimens described in the present paper. The specimens are from West Mineral, Kans. and Shuler Mine in Iowa. They all have been referred to A. glabra and show extreme plasticity of several features of the plant that is correlated with the size of the stem. The major points of difference between A. glabra and A. grayi are now thought to be the presence of distantly spaced nodes in A. glabra, in contrast to closely spaced ones in A. grayi, and the presence of a small amount of mixed tissue in the stele of A. glabra, compared to a large amount in A. grayi. Well preserved axillary branches were found, whose morphology is typically that of the parent stem. It is suggested that the axillary branches were well developed in the species, and that, therefore, several orders of branching may be present in the American material. Successive orders of branching show diminution and simplification which is interpreted as an expression of the presence of determinate growth in the cauline systems of the plant, an ontogenetic pattern that is not commonly found in living forms. AT PRESENT, 2 groups of species have been described in the coenopterid genus Ankyropteris. The first consists of those in which both stems and petioles are known. This seems to be a fairly natural series, despite our ignorance of the upper portions of the fronds and the fructifications of the genus. The primary pinnae are known to have been borne in 2 alternating rows on opposite sides of the petiole (often referred to as the phyllophore in the Coenopteridales). The second group consists of organ species, known only from phyllophore fragments. These are best retained in the same genus as a matter of convenience, since close natural relationships cannot be inferred on the basis of petiolar similarities alone. The taxonomy of both groups of species has been considered by Baxter (1951), while accounts of their anatomy and morphology have been provided by Seward (1910), Scott (1920), Hirmer (1927), and Baxter (1951). HISTORY OF AMERICAN SPECIMENS OF ANKYROPTERIS.-The first report of the genus in American material was in 1938, when A. hendricksi, a silici1 Received for publication January 26, 1959. The author wishes to thank Dr. T. Delevoryas, Dept. of Botany, Yale University, for his advice and guidance throughout the course of this study and for his help in preparing the photographs. The author is also indebted to Dr. W. N. Stewart, Dept. of Botany, University of Illinois, for donating the specimen here referred to as Kansas #1 to our laboratory for study. The Iowa specimens, now in the Paleobotanical Collections of Harvard University, were generously loaned to us by Dr. E. S. Barghoorn, Curator of the collections. fied specimen, was described by Read. In 1941, Darrah reported A. grayi, a species known previously only from the Lower Carboniferous of Europe, as occurring in coal-balls from the Shuler Mine in Iowa. The latter specimens are approximately Middle Pennsylvanian in age, while A. hendricksi, derived from the Johns Valley shale of Oklahoma, is probably Lower Pennsylvanian. The age is somewhat in doubt due to the specimen being an exotic stone, which may have been redeposited from older strata (Read, 1938). The type specimen of A. glabra, described in 1951 by Baxter, was found at Booneville, Indiana, and is of coalball origin. It consisted of a single piece of stem about 30 cm. in length having 4 attached phyllophores. Although the plant was very similar to the European species, A. grayi, it was thought to be distinct on the basis of 2 maj or differences. Whereas A. grayi possesses an integumentary system consisting of a few layers of parenchymatous hypodermis and an epidermis bearing uniseriate hairs, A. glabra, in contrast, was reported as lacking any tissues exterior to the cortical periphery. A difference in nodal anatomy in the 2 species was also reported. In A. grayi, both the phyllophore trace and the axillary branch trace arise from the tangential forking of a common trace, which has arisen from the stele. This is in distinct contrast to the type specimen of A. glabra, where the phyllophore and axillary branch traces have separate origins from the stele. In 1956, an additional specimen from the Booneville site was de-