. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 374 MOSSES AND FERNS CHAP. T. pyxidiferum (Bower (8)), the prothallium remains fila- mentous, and forms a densely branching structure very much like the protonema of some Mosses, but coarser in texture. Other species, however, e. g., T. datum, produced flattened thalloid prothallia from branches of the filamentous forms, and Hymenophyllum always has a flat hepatic-like prothallium, which in its earlier stages, according to Sadebeck ((6), p. i6i), always develops a two-sided apical cell, and di
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 374 MOSSES AND FERNS CHAP. T. pyxidiferum (Bower (8)), the prothallium remains fila- mentous, and forms a densely branching structure very much like the protonema of some Mosses, but coarser in texture. Other species, however, e. g., T. datum, produced flattened thalloid prothallia from branches of the filamentous forms, and Hymenophyllum always has a flat hepatic-like prothallium, which in its earlier stages, according to Sadebeck ((6), p. i6i), always develops a two-sided apical cell, and differs in no wise from that of other Ferns. These prothallia, however, remain single-layered throughout, although they reach an ex- traordinarily large size, and branch much more freely than those of most other Ferns (Fig. 215). The rhizoids are always very short and dark-coloured, and generally occur in. Fig. 215.—Hymenophyllum (sp"). A, Large prothallium of the natural size; B, part of the margin of one of the growing branches, showing two similar initial cells, Xi8o; C, a filamentous male prothallium derived from a bud, X6o. groups upon the margin only. The branching of the prothallia is either monopodial or dichotomous, and the latter method may be repeated a number of times. They may live for an in- definite time apparently. The writer has kept prothallia of both Trichomanes and Hymenophyllum for nearly two years, at the end of which time they showed no diminution of vigour. They form ordinary adventitious shoots, but there are also special gemmae developed in many of them, often in great num- bers. In an undetermined species of Hymenophyllum col- lected in the Hawaiian Islands (Fig. 216) these gemmae oc- curred very abundantly upon prothallia that had ceased to form sexual organs, A marginal cell grows out and curves upward,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and ap
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