The embryology of Larix (1943) The embryology of Larix embryologyoflari194scho Year: 1943 28 ILLINOIS BIOLOGICAL MONOGRAPHS construction to a greater or less degree. In later growth the slight initial advantage for the larger cells becomes increasingly important with refer- ence to selection of the single successful polarity unit. The shape of the archegonial base not only has a considerable in- fluence on the positions of the vertical walls of the proembryo but also on the transverse walls. These are not formed at right angles to the vertical axis of the archegonium but incline downward from
The embryology of Larix (1943) The embryology of Larix embryologyoflari194scho Year: 1943 28 ILLINOIS BIOLOGICAL MONOGRAPHS construction to a greater or less degree. In later growth the slight initial advantage for the larger cells becomes increasingly important with refer- ence to selection of the single successful polarity unit. The shape of the archegonial base not only has a considerable in- fluence on the positions of the vertical walls of the proembryo but also on the transverse walls. These are not formed at right angles to the vertical axis of the archegonium but incline downward from the center to intersect the sides at lower levels. Thus, if the archegonium and vertical rows approximated ideal radial symmetry, the apical cells (lowest tier) of each vertical row would be essentially tetrahedral in form, with one outer side slightly rounded to conform with the basal archegonium wall. As isodiametric an apical cell as possible would be formed. The downward slope of the transverse walls is diagrammatically drawn in Fig. 6 according to this ideal specification. Since only two apical cells (the smaller ones) have a single corner nearest the archegonium center, only these cells approximate the ideal form. The two rows abutting by a straight central wall conform to the shape of the former in that their transverse walls incline downwards from the center, but due to their added width they are more accurately described as asymmetrically wedge- Fig. 6.—Diagrammatic drawing of proembryo in twelve-nucleate stage (8 com- pletely walled cells, 4 open above; only half the total number are shown). Fig. 7.—Longitudinal section of proembryo in same stage as preceding figure. Magnified about 150 times. Collection of May 26, 1933. Fig. 8.—Oblique cross section of proembryo in eight-nucleate stage. Note the arrangement of cells in b, characteristic of proembryos formed in elliptical arche- gonia. Magnified about 140 times. Same collection as Fig. 7. Fig. 9.—Drawing o
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