BRYOPHYTES 
117 
Is rare, and in some cases even sex organs are rare. Therefore, it is 
probable that reproduction is chiefly by vegetative multiplication, which 
may occur as follows : (i) the isolation of branches by the death of 
older axes ; (2) the production of gemmae ; (3) the production of resting 
buds on the protonema, which seem to be only arrested branch buds 
(fig. 251) ; and (4) under appropriate conditions, the development of 
a new protonema from any part of the leafy branch, or from fragments 
of leaves and axes. It follows that a gametophyte once started may 
propagate indefinitely. 
Sex organs. The sex organs are grouped at the end of the main 
stem or of its branches. Around this terminal cluster of sex organs 
the leaves usually become modified in form and 
sometimes in color, forming a sheath or a rosette 
(figs. 252, 253), the whole being the so-called moss 
" flower," a most inappropriate name. The anther- 
idia and archegonia may occur together in the same 
cluster, or they may be in separate clusters, and 
sometimes they are intermixed with multicellular 
hairs (paraphyses). 
In the true mosses the antheridia hold the same 
relation to the apical cell that the archegonia 
hold in the acrogynous Jungermanniales and in 
Sphagnales. The antheridium initials are seg- 
ments of the apical cell, and the apical cell itself 
usually becomes an initial. The growth is by 
means of an apical cell with two cutting faces, and 
the form is usually club-shaped, with a stalk of 
variable length. In discharging the sperms, the 
cells at the apex separate, the mother cells are dis- 
charged en masse, and then the tip cells spring 
together again, so that empty but complete anthe- 
ridia are often observed (fig. 255). 
The archegonia differ from those of the liverworts theridium discharging 
in one important particular. The central cell (pri- s P erm mother cells ' 
. 256, a single sperm. 
mary oogenous cell) does not form all of the axial After SACHS. 
row, which is added to by successive divisions of the 
cap cell. The mature archegonia of mosses are usually more conspicu- 
ously stalked than in the other groups, with more massive venter, and 
with smaller, more numerous, and more ephemeral canal cells (fig. 257). 
FIGS. 255, 256. 
True moss: 255, an an- 
