F, Cavers. 
104 
is detached as a lid. The elaters are well developed, mingled 
irregularly with the spores, and often branched. The spore mother- 
cells, instead of remaining spherical or ovoid as in the other 
Marchantiales (except Monoclea), become deeply divided into four 
lobes (as in Jungermanniales). 
Fig. 13. A.—Transverse section across the anterior end of a fruiting 
plant, showing a nearly mature sporogonium enclosed in its calyptra (cal.) and 
surrounded by the two-lobcd involucre (inv.), the tissue of which contains air- 
chambers at the base (a.c.). Outside of the involucre, two ventral scales (v.s.) 
are shown. The upper part of the section shows the ordinary structure of the 
thallus. x35. B.—Median longitudinal section of a nearly mature sporo¬ 
gonium, showing the spherical capsule, short seta, and bulbous foot. The 
spores and elaters are omitted, to show more clearly the apical patch of fixed 
clater-like cells. x35. C.—Part of B., showing some of the elater-like cells 
at the apex of the capsule, x 300. D.—Part of the ripe capsule-wall, showing 
the annular fibrous bands on the walls of the cells (surface view). x300. 
Cyathodiuni is closely allied to Targionia, and the structural 
differences in the thallus which separate the two genera are chiefly 
