. The structure and development of mosses and ferns (Archegoniatae). y do not all escape at once, but areejected in separate swarms. It is possible that the formationof the separate chambers, noted by the writer, may have some-thing to do with this phenomenon. The development of the archegonium (Fig. 129) is muchlike that of Ophioglossum, but the neck of the archegonium ismuch longer and projects conspicuously above the surface of VII PTERIDOPHYTA-PILICINE^—OPIIIOGLOSSACEJE 24I the thallus. The basal cell also divides more extensively, butthe group of cells derived from it is easily recognisab
. The structure and development of mosses and ferns (Archegoniatae). y do not all escape at once, but areejected in separate swarms. It is possible that the formationof the separate chambers, noted by the writer, may have some-thing to do with this phenomenon. The development of the archegonium (Fig. 129) is muchlike that of Ophioglossum, but the neck of the archegonium ismuch longer and projects conspicuously above the surface of VII PTERIDOPHYTA-PILICINE^—OPIIIOGLOSSACEJE 24I the thallus. The basal cell also divides more extensively, butthe group of cells derived from it is easily recognisable in theripe archegonium. The central cell divides transversely, the lower cell formingthe Qgg, and the ventral canal cell, the up])er one giving riseto the single neck canal cell, whose nucleus later divides as inOphioglossum. The mature ^gg cell contains dense cytoplasm, but has avacuole within it. Jeffrey observed a spermatozoid in the actof penetrating the ^gg, which showed an extension toward theentering spermatozoid. The details of fertilisation, however,. Fig. 129.—Botrychium Virginianum. Development of the archegonium, X about 450. were not made out, but they probably correspond closely withthose observed in other Ferns. Helminthostachys The gametophyte of Helminthostachys (Lang (4)). thethird genus of the Ophioglossacese, does not differ essentiallyfrom the other genera, being also subterranean. It is nearlycylindrical in form (Fig. 126, C). The lower part, which isbrown, and covered with rhizoids, is sterile, and contains an16 242 MOSSES AND FERNS CHAP. endophytic fungus. The upper portion, hghter in colour, bearsthe reproductive organs. Some of the prothalha bear onlyantheridia; the others have archegonia as well. As usual, thefirst antheridia appear before any archegonia are formed. Botharchegonia and antheridia resemble those of Botrychium morethan they do those of Ophioglossiim. The Embryo The fertilised tgg, or oospore, becomes invested with a cell-membrane
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