The structure & development of the mosses and ferns (Archegoniatae) . es, is formedfrom the venter alone, and is tipped with the remains of theneck cells. The position of the archegonium depends largely upon thelight. If both sides of the prothallium are about equallyilluminated, archegonia will develop from both sides. As soonas an archegonium is fertilised, no new ones form, but itfrequently happens that a very large number prove abortivebefore finally fertilisation is effected. The Embryo The first division wall in all Polypodiaceae yet investigatedis vertical and nearly coincident with the
The structure & development of the mosses and ferns (Archegoniatae) . es, is formedfrom the venter alone, and is tipped with the remains of theneck cells. The position of the archegonium depends largely upon thelight. If both sides of the prothallium are about equallyilluminated, archegonia will develop from both sides. As soonas an archegonium is fertilised, no new ones form, but itfrequently happens that a very large number prove abortivebefore finally fertilisation is effected. The Embryo The first division wall in all Polypodiaceae yet investigatedis vertical and nearly coincident with the axis of thearchegonium. This basal wall (Fig. 160, I) at once dividesthe embryo into the anterior epibasal half and the posterior 1 Pfeffer (3). 3i6 MOSSES AND FERNS CHAP. hypobasal. The former produces the stem and cotyledon, thelatter the primary root and foot. The early divisions areextremely regular, and offer a marked contrast to those in theeusporangiate embryo. The second wall is the transverse(quadrant) wall, separating the leaf and stem in the epibasal Fig. i6o.—A, Median longitudinal section of a young embryo of Adiantiim co7icinnuin (H. B. K.)(after Atkinson); B, a four-celled embryo of O. struthiopteris ; C, an older embryo of the samein nearly median section, X250 ; st, stem ; R, primary root; L, cotyledon ; F, foot. part, and the root and foot in the hypobasal. The next wallsare the median or octant walls, but they do not correspondexactly in all the quadrants. While in the cotyledon and stemthey are almost exactly median, in the root especially theoctant wall diverges often a good deal from the median line. X 2>^7 and the two resulting octants arc unequal in size. The follow-ing divisions correspond for a short time in all the octants, butsoon show characteristic differences. For a short time eachoctant shows a definite apical growth, the segments being cutoff by walls formed successively parallel to the three primarydivisi
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
