The structure & development of the mosses and ferns (Archegoniatae) . ercylindrical leaf tapering to a fine point, where the cells aremuch elongated and almost colourless. Its growth is at firstslow, but at a later period (in Pihdaria glolndifera about theeighth day) it begins to grow with great rapidity and soonreaches its full size. This is largely due to a simple elongationand expansion of the cells, which are separated in places, andform a series of longitudinal air-channels separated by radiatingplates of tissue (Fig. 213, i). The simple vascular bundle ^ Arcangeli (l), p. 336. - Hanstein
The structure & development of the mosses and ferns (Archegoniatae) . ercylindrical leaf tapering to a fine point, where the cells aremuch elongated and almost colourless. Its growth is at firstslow, but at a later period (in Pihdaria glolndifera about theeighth day) it begins to grow with great rapidity and soonreaches its full size. This is largely due to a simple elongationand expansion of the cells, which are separated in places, andform a series of longitudinal air-channels separated by radiatingplates of tissue (Fig. 213, i). The simple vascular bundle ^ Arcangeli (l), p. 336. - Hanstein (2). 4o8 MOSSES AND FERNS CHAP. traversine the centre is concentric, with a definite endodermis,but the tracheary tissue is very slightly developed. Thisbecomes first visible about the time the leaf breaks through thecalyptra. The Stem Of the two octants in the stem quadrant one becomes atonce the apical cell of the stem, the other the second leaf,as in other Leptosporangiatae. The first wall in each octantmeets octant and quadrant walls, and cuts off a large cell. Fig. 213.—Longitudinal section of the young sporophyte of Pilularia glohilifcra, still enclosed inthe calyptra {cat), and attached to the macrospore {sp), x 75 ; B, the lower part of the sameembryo, X215 ; r, apical cell of the root ; st, apical cell of the stem; /, lacuna;. from each octant, in contact with the foot. Hanstein andArcangeli regard these as part of the foot, and physiologicallythey no doubt are to be so considered, but morphologically theyare beyond question segments respectively of the stem and secondleaf. At first these are not distinguishable from each other, butthe divisions in the latter are usually (in Pilularia) less regular,and the apical cell early lost. It may, however, develop aregular three-sided apical cell, like that of the later earlier segments of the stem apex are larger than thesubsequent ones, and the broadly tetrahedral form of the XII LEPTOSPORANGIATyi: HETEROSPORE^E
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
