The structure & development of the mosses and ferns (Archegoniatae) . which is not so well developed, however,as in the latter. The originally one-layered archesporium laterbecomes double, and as in Sphagnum extends completely overthe columella, which is thus not continuous with the tissue ofthe upper part of the sporogonium. As in Sphagnum also, notrace of the intercellular space formed in the amphithecium ofthe Bryineae can be detected. A section of the nearly ripecapsule shows the club-shaped columella extending nearly tothe top of the cavity. With the growth of the capsule the 1 Waldner (2
The structure & development of the mosses and ferns (Archegoniatae) . which is not so well developed, however,as in the latter. The originally one-layered archesporium laterbecomes double, and as in Sphagnum extends completely overthe columella, which is thus not continuous with the tissue ofthe upper part of the sporogonium. As in Sphagnum also, notrace of the intercellular space formed in the amphithecium ofthe Bryineae can be detected. A section of the nearly ripecapsule shows the club-shaped columella extending nearly tothe top of the cavity. With the growth of the capsule the 1 Waldner (2). VI MOSSES {MUSCl): SPHAGNACEAi—^ space between the inner and outer spore-sacs becomes very-large to accommodate the growth of the numerous pseudopodium is exactly the same as in Sphagmun, andthe vaginula and calyptra are present. The latter is muchfirmer than in Sphagnum, and like that of the Bryineai. ArcJiidium The genus ArcJiidium is one whose systematic position hasbeen long a subject of controversy. It has usually been associated. Fig. 84.—Archidhiin Ravcnclii (Aust.)- A, Median section through a nearly ripe sporogonium, X 90 ; B, base of the sporogonium, x 270. with the so-called cleistocarpous Bryineai, but the researches ofLeitgeb seem to point to a nearer affinity with Andrecea. The species of ArcJiidium are small Mosses growing on theearth, and especially characterised by the small number, butvery large size, of the spores contained in the sessile globularsporogonium. Hofmeister ^ was the first to study the develop- ^ Hofmeister (i), p. 178 MOSSES AND FERNS chap. ment, and his account agrees in the main with Leitgebs/except as to the relation of the columella and outer first divisions in the embryo correspond exactly to thosein AndrecBa and the Bryineae, and for a time the young embryogrows from a two-sided apical cell. The secondary divisionsin the segments, however, are quite different from that observedin any oth
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