. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. THE EMBRYO 35 fairly complete series of embryos was obtained and the development followed quite satisfactorily. In O. moluccanum I found two quite young embryos, the youngest consisting of two cells (fig. 18, B), the other much more advanced, with the cotyledon already differentiated and the beginning of the primary root recognizable. In the first embryo the basal wall was nearly transverse to the axis of the archegonium and, to judge from the arrangement of the organs of th
. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. THE EMBRYO 35 fairly complete series of embryos was obtained and the development followed quite satisfactorily. In O. moluccanum I found two quite young embryos, the youngest consisting of two cells (fig. 18, B), the other much more advanced, with the cotyledon already differentiated and the beginning of the primary root recognizable. In the first embryo the basal wall was nearly transverse to the axis of the archegonium and, to judge from the arrangement of the organs of the older embryo, it looks as if the whole of the hypobasal region formed the foot, the epibasal half giving rise to the cotyledon and root. The older embryo (fig. i8, C) was cut longitudinally in the plane of the cotyledon, which at this time comprises pretty much the whole of the upper part of the embryo, the hypobasal region being occupied mainly by large cells which con- stitute the foot. Unfortunately, in this series the section containing the apex of the leaf was missing, and so it is impossible to say whether at this stage a definite apical cell is present in the cotyledon; but, as in somewhat older stages such a cell seemed to be always present, it is probable that there was an apical cell in the cotyledon of the embryo in question. At the base of the leaf, and almost in the center of the embryo, there was a group of actively growing cells, evidently marking the position of the root apex, which arises deep in the tissue of the embryo, very much as we shall see to be the case in the Marattiaceae; and it seems probable that in 0. moluc- canum, as in Dancea, the root grows downward through the foot and in a direction coincident with the axis of the young Fig. 19.—Ophioglossum vulgatum (after Bruchmann). A. Median section of a young embryo. Xi6o. B. An older embryo. X25. C, D. Older embryos, showing beginning of apical bud, b; r, root. X25. The cotyledon grows u
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