. The structure and development of mosses and ferns (Archegoniatae). veringthe top of the columella. In nearly related genera, however,e. g., Weisia, a genuine peristome is present. The Tetraphidese, represented by the genus Tetraphis(Georgia) (Fig. 118), are interesting as showing the possibleorigin of the peristome, as well as some other interesting points ^ This seems to be strictly the case only in the smaller branches; in thelarges axes the leaves are not exactly in three rows. w. THE BRYALES ±1^ of structure. Tetraphis pellucida is a small Moss, which atthe apex of its vegetative branche
. The structure and development of mosses and ferns (Archegoniatae). veringthe top of the columella. In nearly related genera, however,e. g., Weisia, a genuine peristome is present. The Tetraphidese, represented by the genus Tetraphis(Georgia) (Fig. 118), are interesting as showing the possibleorigin of the peristome, as well as some other interesting points ^ This seems to be strictly the case only in the smaller branches; in thelarges axes the leaves are not exactly in three rows. w. THE BRYALES ±1^ of structure. Tetraphis pellucida is a small Moss, which atthe apex of its vegetative branches bears peculiar receptaclescontaining multicellular gemmae of a very characteristic leaves that form the receptacle are smaller than the stemleaves, and closely set so as to form a sort of cup in which thegemmae are produced in large numbers. These arise as slendermulticellular hairs, the end cell of which enlarges and forms adisc, at first one-layered, but later, by the walls parallel to thebroad surfaces, becoming thicker in the middle, and lenticular. Fig. ii8.—Tetraphis pellucida. A, Plant with gemmae, X6; B, upper part of thesame, X50; C, young gemma, X600; D, a fully-developed gemma, X300. in form. The arrangement of the cells in the young gemmaelooks as if the growth of the bud was due to a two-sided apicalcell (Fig. 118, C), but this point was not positively gemmae give rise to a protonema of a peculiar form, fromwhich in the usual way the leafy stems develop. The proto-nemal filaments grow into flat thalloid expansions that recallthose of Sphagnum and Andrecua. 220 MOSSES AND FERNS CHAP, The sporogonium of Tetraphis has a peristome of pecuHarstructure, and not strictly comparable to that of any of theother Mosses. After the operculum falls off the tissue lyingbeneath splits into four pointed teeth, which, however, are not,as in Funaria, composed simply of the cell walls, but are massesof tissue. All the other higher Bryales, with the excep
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