The structure & development of the mosses and ferns (Archegoniatae) . hows a single very ^ Bower (11), pp. 310, 314. Van Tieghem and Douliot (5), p. 378. ^ Lachmann (i) asserts, however, that he found a group of initials such as Bowerdescribes. XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 355 lari^c initial, more or less triangular in form when seen inprofile, but with the point sometimes truncate. Transversesections show that it is really a four-sided pyramid. Theyoung segments are very large, and it is possible that thesemay sometimes assume the role of initials. Owing to theslowness and irregularity
The structure & development of the mosses and ferns (Archegoniatae) . hows a single very ^ Bower (11), pp. 310, 314. Van Tieghem and Douliot (5), p. 378. ^ Lachmann (i) asserts, however, that he found a group of initials such as Bowerdescribes. XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 355 lari^c initial, more or less triangular in form when seen inprofile, but with the point sometimes truncate. Transversesections show that it is really a four-sided pyramid. Theyoung segments are very large, and it is possible that thesemay sometimes assume the role of initials. Owing to theslowness and irregularity of cell division it is difficult to tracethe limits of the segments beyond the youngest ones. Theyusually form a spiral, but cases were sometimes encounteredwhere the segments were apparently cut off in pairs fromopposite sides of the initial cell. The root-cap arises in partfrom special segments cut off from the outer face of the apicalcell, but also in part from the outer cells of the lateral segments,as in the Eusporangiatse. The separation of the tissue system. Fig. 183.—Osimmda regalis (L.). A, Section of young sporophyll passing through three veryyoung sporangia; B, longitudinal section of an older sporangium ; t, the tapetum, x 325 (afterBower). follows much as in Botryclduni. The plerome cylinder is largeand oval in section, but with poorly-defined limits, and it isnot possible to state positively whether it owes its originexclusively to the innermost cells of the segments. The largecentral tracheae, as in Adiantuni, are very early Claytoniana agrees on the whole with O. cinnamomea, butthe divisions are much more regular, and it approaches nearerthe typical leptosporangiate type, both in the arrangement ofthe young tissues and the structure of the fully-developedvascular bundle, which closely resembles that of the Polypodi-aceae, and differs from the investigated species of Osnninda andTodea in the better development of the endodermis, and inhaving
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