A crogyn ous Jungerm anniales . 277 
The antheridia (Fig. 52, B, C), which are spherical or ovoid with a 
slender stalk, are borne in the axils of more or less modified “ male 
bracts” (perigonial leaves), either singly or in groups of from two 
to about twelve; they are sometimes ( Scapania , etc.) accompanied 
by filamentous or narrow leaf-like paraphyses. The perigonial 
leaves are always simple and symmetrical in form, even in species 
where the ordinary leaves are deeply divided into lobes differing 
greatly in size and shape and show other modifications (water-sacs, 
etc.). The antheridia are seldom borne in the axils of the under¬ 
leaves where these are present, and they are often produced on 
special short catkin-like branches, the “ male bracts ” being crowded 
and often having saccate bases for the better protection of, and 
especially the retention of moisture about, the antheridia. 
The archegonia are borne in terminal groups at the apex of the 
main axis, or of its ordinary branches, or of special short branches 
—the latter often arising from the underside of the stem. In any 
case, the development of an archegonial group—probably that of 
the first archegonium in the group—uses up the apical cell and thus 
terminates the growth of the stem. In the Lejeuneas a single 
archegonium is developed, and in Frullania (Fig. 52, D, E) only two 
or three, but in most cases the group contains a large number 
(sometimes a hundred or more) though as a rule a single mature 
sporogonium is produced. The archegonial group is surrounded by 
an “involucre” or “ perichaetium ” consisting of leaves which 
usually differ in their larger size and in other respects from the 
ordinary vegetative leaves. The archegonial branch generally tends 
to grow erect, and the underleaves (“bracteoles”) of the “involucre” 
are then nearly or quite as large as the leaves (“ bracts ”) and are 
usually present even in species which lack underleaves on the rest 
of the shoot. The bracts are often more extensively laciniated and 
fringed than the vegetative leaves, as an adaptation for retaining 
moisture by capillarity, but on the whole they are, throughout the 
Acrogynae, less specialised than the leaves. For instance, they are 
usually divided symmetrically by a median notch of greater or less 
depth, alike in species with entire rounded leaves and in those 
with the leaves cleft into a larger and a smaller lobe, and they 
never show special structures like water-sacs. 
In the great majority of Acrogynae, the archegonial group 
becomes surrounded by a tubular organ—the “ perianth ”—which 
arises within the involucre, making its appearance after the 
development of the archegonia themselves. As a rule, the formation 
