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

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Abstract
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 A. grayi, originally a Lower Carboniferous species from England, and to A. glabra, a Middle‐Pennsylvanian 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.