Abstract

The organography and anatomy of the sporeling of Ceratopteris (C. thalictroides and C. pteri doides) are described. Unlike the adult sporophyte which has a greatly reduced stem known as the leafy stem, the sporeling of this fern has an elongated, more or less erect stem with nodes and internodes. It is snggested that light is an important factor affecting the internode elongation. The major parts of the plant body in the sporeling are: primary root, adventitious root, node, internode, hypocotyl, epicotyl, cotyledon, leaf, and terminal bud. The vascular system is extremely simple; only a single strand of vascular tissnes runs through the whole plant body except in the laminum where the bundle forins a network. The stele is a protostele. Evidence is presented showing that the plant body of the sporeling is an aggregation of phytons. The adult phytons, each of which has a complete set of the three fundamental parts (i.e., leaf, stein, and root), are joined one after another with the short interconnecting strand of vascular tissues. The nature and origin of the interconnecting vascular strand are described. The stein of the phyton, which is morphologically the basal part of the leaf, contributes as an internode to constitute the whole plant body. The sporophyte of this fern is thus considered to be a complex organism. The new phytons are derived from the apical phyton iniţial, or the apical cell of the shoot which is located at the extreme tip of the shoot apex. It is suggested that the apical phyton initial is closely homologous to the zygote, and the apical meristem of the shoot to the young embryo. From this it is further suggested that the embryo at the quadrant stage consists of the apical phyton initial, the two.celled cotyledonary phyton (one cell gives rise to the cotyledon and primary root, and one cell to foot), and the one-celled first phyton. The newly formed juvenile phytons as well as the apical phyton initial are nutritionally and probably hormonally dependent on the prothallus and adult phytons.