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Numerous specimens from several species of the Paleozoic marattialean fern genus Psaronius Cotta were collected from Upper and Middle Pennsylvanian deposits in Ohio, Illinois, and Kansas. I suggest that, as the Psaronius plant grew, basal portions of the stem and bound root zone decayed. This conclusion is based on specimens in which the stem and bound root zone are completely or partially lacking, the paucity of very basal trunk segments known for the genus, and evidence from living analogs. Secondary parenchyma in P. chasei Morgan and P. blicklei Morgan is described as localized areas of radially aligned cells in stems and outer cortex. Linear regressions of number of orthostichies, stelar cycles, and inner meristeles versus stem diameter indicate that vascular ontogeny may have occurred at different rates among some species of Psaronius. Analysis of Psaronius stem anatomy and morphology suggests that, in general, stems had an open, unidirectional growth mode with a continuously expanding apex and vascu...

1. A well-preserved silicified specimen of the genus Psaronius, showing both the internal anatomy and the external features of Caulopteris, is described (as P. cooksonii) from the Kansas Wabaunsee group, Upper Pennsylvanian. 2. Anatomically, it is characterized by twelve foliar bundles alternating with twelve peripheral bundles. The leaf scars are in twelve vertical rows arranged in alternating whorls of six leaves each. Evidence is presented to show that the pattern of the leaf trace scar varies (depending on the distance from the base of the petiole) from a straight band to a U-shape, then to an oval-shape, and finally to an oval with an inclosed inverted V. It is also pointed out that when the Caulopteris surface is free from the usual sheath of adventitious roots, the leaf vascular bundle scar is visible only as a slightly curved band within the base of the protruding petiole scar, its higher configurations being simulated by the fissure between inner parenchyma and outer sclerotic zones of the petiole.

1. Some isolated vegetative fragments of two groups of Carboniferous plants, Sphenophyllum and Psaronius, are described. The fragments are from different sources, from Indiana, Illinois, and Texas, but all are from coal fields which were said to be part of the Allegheny formation of the Pennsylvanian system. 2. The Sphenophyllum fragments consist of stem tips, their associated leaves, and small portions of two mature stems. One of the mature stems is noteworthy for its exceptional size, measuring 1.5 cm. in diameter, which makes it one of the largest, if not the largest, on record. This stem also possesses irregularities of growth simulating growth rings. 3. A review of the anatomical features of the different regions of Sphenophyllum leads to the belief that the plant was of a trailing or scrambling (lianoid) habit. 4. Adventitious rootlets from two regions of Psaronius are described: (a) young rootlets from the upper region of the stem, where they are crowded and held together by interstitial tissue, ha...

1. This paper records the occurrence of a number of plants found as petrifacts from Calhoun coal mine, Richland County, Illinois. The plants belong to the genera Calamites, Sphenophyllum, Lepidodendron, Lepidostrobus, Sigillaria, Mazocarpon, Botryopteris, Anachoropteris, Psaronius, Heterangium, Myeloxylon, and Cardiocarpus. 2. It appears that there are no constant anatomical distinctions between the Eu-Sigillariae and the Sub-Sigillariae. 3. The branching of petioles of Botryopteris americana is described.

1. A morphological study of four specimens of the Paleozoic tree fern Psaronius was made. These specimens were placed in the following three species: Psaronius septangulatus Gillette, P. peoriensis Gillette, and P. giffordi Potonie. P. sepiangulatus and P. peoriensis possessed seven rows of leaves arranged spirally; P. giffordi possessed six rows of leaves arranged in two whorls. 2. The vascular anatomy of one of the specimens of Psaronius septangulatus was studied in detail from a series of transverse sections of the stem. The leaf traces diverge outward from the center of the stem axis in a manner somewhat similar to that described for P. infarctus, which possessed whorled leaves. 3. Thin sections of all three species were examined and described for the different tissue types.