. The structure and development of mosses and ferns (Archegoniatae). he usual way. The gametophore itself, es-pecially where it is large and long lived, by the separation ofits branches rapidly increases the number of new is especially marked in Sphagnum, where this is theprincipal method of propagating the plants. Special organsof propagation in the form of gemmse also occur, and thesemay develop from the protonema or from the gametophoreTetraphis pellucida (Fig. 118) is a good example, showingthese specialised gemmse which after a time germinate by V. MOSSES (MUSCI): SPHAGNA
. The structure and development of mosses and ferns (Archegoniatae). he usual way. The gametophore itself, es-pecially where it is large and long lived, by the separation ofits branches rapidly increases the number of new is especially marked in Sphagnum, where this is theprincipal method of propagating the plants. Special organsof propagation in the form of gemmse also occur, and thesemay develop from the protonema or from the gametophoreTetraphis pellucida (Fig. 118) is a good example, showingthese specialised gemmse which after a time germinate by V. MOSSES (MUSCI): SPHAGNALES—ANDRE/HALES 163 giving rise to a protonema upon which, as usual, the gameto-phore arises as a bud. In size the gametophore of the Mossesranges from a milHmetre or less in height in Biixbaiimia andEphemerum to 30 to 50 cm. in the large Polytrichacese andFontinalis. The branching of the gametophore. is neverdichotomous, and so far as is known the lateral branches arise,not in the axils of the leaves, but below them. Underground t , C^ %v ^ /IS <i^-. Fig. 86.—Climacium Americanum, showing the formation of stolons, Xi» Stems or stolons, which afterwards develop into normal leafyaxes, are common in many forms, e. g., Climacium (Fig. 86).The sexual organs are borne either separately or togetherat the summit of the gametophoric branches. Where theplants are dioecious, it sometimes happens that the two sexesdo not grow near together, in which case, although archegonia i64 MOSSES AND FERNS CHAP. may be plentiful, they fail to be fecundated and thus no cap-sules are developed. This no doubt accounts for the extremerarity of the sporogonium in many Mosses, although in othercases, e. g., Sphagnum, it would appear that the formation ofthe sexual organs is a rare occurrence. These resemble in gen-eral those of the Hepaticse, but differ in some of their leaves surrounding them are often somewhat modified,and in the case of the male plants (Atrichum, Polytrichum)differe
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