tained both filamentous and granular inclusions, while the inclusions of the cells undergoing meiosis were generally granular. A compact mitochondrial plate was formed between the daughter nuclei of the first meiotic division. Senjaninova (1927) described in N ephrodium a similar transformation of rod-like mitochondrial bodies of the earlier stages into granular inclusions of the spore-mother cell. It was stated that in the fully-rounded sporocyte, most of the mitochondria were on one side of the nucleus, as was most of the cytoplasm. At a later stage, a remarkably regular behavior of the granules occurred, and at diakinesis, four distinct groups of granules were observed. Following the separation of the chromosomes at the first meiotic division, the granules formed a compact plate, interposed between the daughter nuclei, in much the same manner as described by Lewitsky in Equisetum. This plate was split by the formation of the cell walls of the newly-formed spores, and as the second division was completed, each spore received approximately one-quarter of the granules. Lenoir (1934) observed essentially the same pattern of behavior on the part of inclusions in living spore-mother cells of Equisetum.Kirby (1928) studied the development of chloroplasts in the spores of Osmunda. This work gives no account of any regular behavior of granules preceding and during meiosis. She states that in Osmunda, the chloroplasts are probably produced from mitochondria which are homologous with those of animals. The production of spores with abnormal pale chloroplasts from normal green sporophyte areas was reported by Andersson (1923) in a study of the genetics of variegation in Adiantum. The cytological history of these abnormal plastids, however, was not described.MATERIALS AND METHoDs.-Materials used in the present study consisted of fertile fronds of Onoclea sensibilis collected at various stages of sporangium formation and sporogenesis. These were treated according to cytological procedures described below, and as far as possible, observations on fixed materials were paralleled by study of living, unstained cells. Nine cytological fixing procedures were used in this study. Osmic impregnation methods included that of Kolatchev (Bowen, 1929), a method suggested by Baker (1945), Newcomer's method for osmic impregnation of plant inclusions (Newcomer, 1940), and O'Brien's modification of Zirkle's fixative (O'Brien, 1942) followed by treatment with osmium tetroxide. Aoyama's silver method for Golgi as described by Baker (1945) was also tried.. The methods used to demonstrate mitochondrial inclusions were those of Regaud (Lee, 1937), Lewitsky (1925), and Huseby (1946). Flemmlng's 603 STUDIES DEALING with the cytoplasmic i\Jclusions of the sporogenous cells, spore-mother cells, and developing spores of the Pteridophyta have appeared with relative infrequence in the botanical and cytological literature. In several of the more detailed accounts published (Lewitsky, 1925; Senjaninova, 1927) the meiotic divisions of the sporemother cel...