The structure & development of the mosses and ferns (Archegoniatae) . rapiddivision in all directions forms a large mass of cells whosecontents become denser than those of the surrounding ones,between which and these, however, the limits are not very , when the number of cells is complete, the difference 2^.8 MOSSES AND FERNS CHAP. between them and the sterile tissue of the sporangiophore ismuch more evident. The cells lying outside of the archesporium divide rapidlyboth by longitudinal and transverse walls, and form the thickouter wall of the sporangium. In longitudinal sections, t
The structure & development of the mosses and ferns (Archegoniatae) . rapiddivision in all directions forms a large mass of cells whosecontents become denser than those of the surrounding ones,between which and these, however, the limits are not very , when the number of cells is complete, the difference 2^.8 MOSSES AND FERNS CHAP. between them and the sterile tissue of the sporangiophore ismuch more evident. The cells lying outside of the archesporium divide rapidlyboth by longitudinal and transverse walls, and form the thickouter wall of the sporangium. In longitudinal sections, tworows of cells may be seen extending from the mass of arche-sporial cells to the periphery. In these rows the vertical wallshave been more numerous than in the adjacent ones, so that. 7ic. i2-L.—Oj>hioglossumfiendiilutn {). A, Young sporangium in longitudinal section, X22S. Thearchesporial cells are shaded, the double line of cells shows where the sporangium opens ; B, partof the sporogenous tissue from an older sporangium, X 225 ; C, cross-section of a nearly full-grownsporangiophore, X15. the number of cells in these rows is greater. It is betweenthese rows of cells that the cleft is formed by which the ripesporangium opens. The cells of the ground-tissue adjoiningthe archesporium divide into several layers of narrow cells,which form the tapetum. After the full number of cells is reached in the archesporium,their walls become partially disorganised, and the cells round VIII THE PTERIDOPHYTA—OPHIOGLOSSACEyE 239 off and separate, exactly as in the sporogonium of a Bryophyte,and each cell is, potentially at least, a spore mother ^ states that only a part of the cells produce spores, andthat the rest remain sterile and serve with the disorganised
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
