Bryophytes : Liverworts and Mosses 



475 



archegonium is a multicellular, flask-shaped body in which a 

 single large egg is formed at the base of the neck. These 



Fig. 2gi. Sphagnum moss: A, upright shoot, with antheridial branches above and two 

 archegonial branches below ; B, prothallus with young sporophyte ; C, archegonial branch 

 with mature sporophyte ; D, archegonia within the scales of the archegonial branch ; E, tip 

 of archegonial branch and the attached sporophyte seen in section. The old archegonium 

 wall still surrounds the sporangium. {After Frank.) 



organs may be on the same branch tip or on different branches. 

 The sperms are discharged from the antheridium by the absorp- 

 tion of water and consequent bursting when the moss is wet. 

 The sperms swim about in the film of water on top of the plants. 

 Some reach the archegonia and fertilization follows. The in- 

 terior row of cells (neck-canal cells) of the archegonium (Fig. 290) 

 disintegrate as the egg matures and form a mucilaginous mass 

 from which sugars diffuse into the water. When this diffusing 

 sugar reaches the swimming sperms, their direction of swimming 

 is changed toward the diffusing sugar and in this way they swim 

 into the archegonium and one finally reaches the egg and fuses 

 with it. When the sperm unites with the egg, it forms an oospore. 

 The protonema and the leafy branches that arise from the 

 spore make up the gametophyte generation of the moss. 

 Generally the gametophyte is perennial and gametes are produced 

 each year from new branches. 



