. The structure and development of mosses and ferns (Archegoniatae). arily would produce theventral lobe of a leaf, formsthe rudiment of the branch,so that the leaf, in whose axilthe branch stands, has onlythe dorsal lobe developed. Inthe other case, only a part ofthe cell is devoted to formingthe branch, and the rest formsa diminished but evidentventral leaf-lobe, inaxil the young branch is situ-ated. The formation of theintercalary branches, whichare for the most part of endogenous origin, may be illustratedby Mastigohryum, wdiere the characteristic flagellate branchesarise in this manner. T
. The structure and development of mosses and ferns (Archegoniatae). arily would produce theventral lobe of a leaf, formsthe rudiment of the branch,so that the leaf, in whose axilthe branch stands, has onlythe dorsal lobe developed. Inthe other case, only a part ofthe cell is devoted to formingthe branch, and the rest formsa diminished but evidentventral leaf-lobe, inaxil the young branch is situ-ated. The formation of theintercalary branches, whichare for the most part of endogenous origin, may be illustratedby Mastigohryum, wdiere the characteristic flagellate branchesarise in this manner. The apical cell of the future branch(the branches in this case arise in strictly acropetal order)springs from the ventral segment, and exactly in the is distinguished by its large size, and is covered by a singlelayer of cells (Fig. 61). In this cell the first divisions estab-lish the apical cell, wdiich then grows in the usual way. Theyoung bud early separates at the apex from the overlying cells,which rapidly grow, and form a dome-shaped sheath, between. I „„p Fig. 61.—Mastigobryum trilobatum. Longi-tudinal section of the stem, showingthe endogenous origin of the branches;X, the apical cell of the branch, X24S(after Leitgeb). ii8 MOSSES AND FERNS CHAP, which and the bud there is a space of some size. Later theyoung branch grows more rapidly than the sheath and breaksthrough it. The non-sexual reproduction of the acrogynous Hepatlcsemay be brought about either by the separation of ordinarybranches through the dying away of the older parts of thestem, or in a few cases observed (Schiffner (i), p. 67) newplants may arise directly from almost any point of a leaf or stem. Gemmae are known in alarge number of species. Thesein most of the better knowncases are very simple unicellularor bicellular buds arising oftenin great numbers, especiallyfrom the margins and apices ofleaves. Curious discoid multi-cellular gemmse have been dis-covered in a number of species,especia
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
