The structure & development of the mosses and ferns (Archegoniatae) . special walls, the mothercells of the root-hairs (Ji). Van Tieghem ^ states that the secondary roots arise fromthe pericycle instead of from the endodermis, as in otherPteridophytes, but Strasburger claims that the so-called peri-cycle of Lycopodium is really cortical, and does not belongproperly to the central cylinder, so that this difference is onlyapparent. The endodermis itself is not readily recognisableon account of the complete cutinisation of the walls. The origin of the root-hairs is somewhat peculiar. Fromthe base
The structure & development of the mosses and ferns (Archegoniatae) . special walls, the mothercells of the root-hairs (Ji). Van Tieghem ^ states that the secondary roots arise fromthe pericycle instead of from the endodermis, as in otherPteridophytes, but Strasburger claims that the so-called peri-cycle of Lycopodium is really cortical, and does not belongproperly to the central cylinder, so that this difference is onlyapparent. The endodermis itself is not readily recognisableon account of the complete cutinisation of the walls. The origin of the root-hairs is somewhat peculiar. Fromthe base of each dermatogen cell a wedge-shaped cell is cutoff (Fig. 247, C, Ji), and this afterwards is divided into twosimilar cells, each of which grows out into a unicellular the root-hairs are found in pairs. The roots always normally branch dichotomously, as inIsoetes, and the successive divisions usually are in planes atright angles to each other. As in Isoetes, the process is in- ^ Strasburger (10), p. 259. ^ Van Tieghem (5), p. 553. XIV L YCOPODINE^E 475. .s^ augurated by a broadening of the apex of the root, which isfollowed by a forking of the plerome and a subsequent divisionof the other histogenic tissues. The structure of the mature root ^ in L. clavatiun, , and most species examined, is much like the hexarch to decarch fibrovascular cylinder is radial instructure, the xylem plates oftenunited at the centre, so thatin cross-section they present amore or less regular stellateform. In L. selago and L. in-undatuju, according to Russow,^the xylem is diarch and the twomasses united into a single one,which is crescent-shaped in sec-tion, with the phloem occupyingthe space between the extremi-ties. As in the stem the primarytracheids are narrow annularand spiral ones, and the largesecondary ones scalariform. Gemmcs Special bulblets or gemmaeare formed regularly in a numberof species of Lycopodiiun, andhave been the subject of severalspecial investigat
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
