コシダおよびウラジロの生長点にっいて

Abstract

The structure of the apical meristems, the formations of lateral organs and the tissue differentiation were studied in rhizomes of Dicranopteris dichotoma and Diplopterygium glaucum.1. In both species, there is an apical dome at the tip of the rhizome, and a single well-defined apical cell is located at the summit of the apical dome. The apical meristem consists of the following zones; (1) the apical segmentation zone (SZ) consisting of an apical cell and its immediate segment cells, (2) mother cells zone of the stele (MS) which differentiates into the stelar tissue having no pith in these species and consisting of meristematic cells arranged in sereval parabolic rows beneath the segmentation zone, (3) mother cell zone of the cortex (MC) located laterally to the above two zones, consisting of cells thick-walled and rich in cell contents. The lowest discernible parabolic row in MS and its extension through the cortical area to the surface of the stem were tentatively defined as a boundary of the apical meristem.2. The foliar primordium has an apical cell on its tip, which originates from one of the apical segments. The foliar apical cell is at first rectangular in longitudinal dorsiventral section, then becomes triangular with convex free surface, and finally hemispherical. In transverse view, it has at first four cutting faces, then becomes lenticular with one of its edge toward the apical cell of the stem. The differentiation of the leaf trace procambium is always acropetal and continuous with the vascular system of the stem. No foliar gap is formed in these species.3. The structure of the apical meristem of the lateral but is essentially the same with that of the main stem in both species. The initiation of the lateral bud was studied in details with Dicr. dichotoma in which buds arise on the dorsal side of the rhizome alternately with leaves. Its apical cell originates from one of the apical segments just as in the case of the initiation of the foliar apical cell. It formes a segmentation zone around it by lateral divisions. It may be concluded that at least in Dicr. dichotoma the branching is monopodial from the view points of its initiation and the mode of vascular supply from the main stem. The author wishes to express his thanks to Prof. H. Ito of the Tokyo Kyoiku University for his valuable suggestion and criticism.