Bryales . 31 
Fig. 70 .—Tetraphis pellucida. I. Upper portion of ripe capsule, with four 
peristome teeth ; above is the detached operculum. II. Transverse section 
of young capsule, taken above th$ annulus-; the four central cells (columella 
portion of the operculum) have already split apart. III. Transverse section 
of upper portion of nearly ripe capsule ; the outermost layer of cells forms 
the operculum. IV. Transverse section of operculum and peristome of ripe 
capsule, in which the operculum has become loosened and the four teeth have 
split apart. II. and III. from Goebel. 
(Tetraphidineae), the Polytrichaceae and Dawsoniaceae as a third 
(Polytrichineae), the remaining Bryales being placed in his group 
Eu-Bryineae. It would seem better to raise Fleischer’s sub-groups 
of Bryales into independent groups—Tetraphidales, Polytrichales, 
Buxbaumiales, and Eu-Bryales. These groups may be briefly 
characterised as follows:— 
I. Tetraphidales. Peristome consists of four solid pyramidal 
cell-masses, formed by the splitting, along two intersecting radial 
planes, of the entire tissue lying within the single-layered lid 
(operculum) of the capsule. The group comprises two orders— 
Tetraphidaceae with the genera Tetraphis and Tetradontium and 
Calomniaceae with the genus Calomnium (with a single tropical 
epiphytic species). Calomnium has no peristome, but otherwise it 
closely resembles Tetraphis ; for instance, its rhizoids, which grow 
on the aerial roots and stems of Ferns, produce erect branched leaf¬ 
like assimilating organs similar to those borne on the protonema of 
Tetraphis. 
The peculiar and probably primitive peristome of Tetraphis may 
in some respects be compared with the elaterophore of Aneura and 
Metzgeria among the Jungermanniales, since the four intersecting 
cleavage lines appear in the apical tissue of the capsule at an early 
stage in development (see Fig. 70). 
II. Polytrichales. Peristome arises in the inner zone of 
the amphithecium, consisting of a variable number of cell-layers, 
and the teeth (typically U-shaped at the base) are formed from 
entire cells arranged in rows or bundles. In Dawsonia the 
peristome-forming zone is broad, and the peristome consists of 
numerous long filaments (single cell-rows or bundles of cell-rows) 
which become separated by resorption of the intervening thin-walled 
tissue of this zone. In Polytrichaceae the peristome arises from a 
single annular series of cells, in which curved dividing walls appear 
in such a way as to form bundles constituting a ring of thirty-two 
or sixty-four (rarely sixteen) short pyramidal teeth; the tips of these 
are joined to a thin membrane (epiphragm) formed by the basal 
tissue of the columella in the operculum, and a poppy-like 
