LIFE HISTORY OF A MOSS 
199 
occurs together in a group on a single female branch. A 
number of enlarged leaves surrounding the archegonia con- 
stitute a perichatium. The antheridial and archegonial 
branches at first occur close together near the summit of 
the branch, but the branch often elon- 
gates in the region between the two, 
thus separating them. 
182. Asexual Multiplication. One 
of the sterile branches, near the apex 
of the plant, usually develops more 
strongly than the others, and each year 
the old stem below dies off, and the 
young branch becomes established as a 
new plant. Under favorable condi- 
tions young plantlets, called innovation 
branches, may develop on the sterile 
branches, at the tip and back from the 
tip, strike root, and become established 
as independent plants (Fig. 144). 
183. Sexual Reproduction. Fertili- 
zation is accomplished in a manner 
similar to that in the fern, a film of 
water being required in order that the 
motile sperm may swim to the neck-canal, down which it 
passes, to the venter and into the egg, where the two nuclei 
unite. Fertilization probably occurs, as a rule, in winter, 
for young embryos are usually found in very early spring. 
The first division-wall of the oosperm is horizontal, or 
nearly at right angles to the axis of the neck, and thus 
at right angles to the position of the wall in the first divi- 
sion of the leptosporangiate ferns. As the cell-divisions 
follow each other in rapid succession, the upper cells 
FIG. 144. Sphag- 
num cuspidatum, 
showing innovation, 
or short, branches. 
(After Schimper.) 
