LLFE HISTORY OF A MOSS 



199 



occur* together in a group on a single female branch. A 

 number of enlarged leaves surrounding the archegonia con- 

 stitute a perichcBtium. 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 estabhshed 

 as independent plants (Fig. 144). 



183. Sexual Reproduction. — Fertili- 

 zation is accomplished in a maimer 

 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 v6nter 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 cttspidatum, 

 showing innovation, 

 or short, branches. 

 (After Schimper.) 



