[Chap. XLVIIl 



MOSSES AND LIVERWORTS 



647 



them. Scattered among the antheridia and archegonia may be numerous 

 sterile filaments. 



Fig. 298. A moss plant (Mniitm). E represents a vegetative branch, B a female 

 branch, and A a male branch. After fertilization, an upright stalk bearing a spore 

 case (C) develops from the zygote. A' represents a longitudinal section of the tip 

 of a female branch bearing three archegonia each of which contains an egg; B' 

 represents a section of the tip of a male branch bearing three antheridia each of 

 which contains manv sperms. Courtesv of World Book Co. 



When a mature antheridium absorbs so much water that it swells and 

 bursts, the sperms are set free. Since they are motile the^■ swim about in 

 the film of water on top of the plant or mass of plants, and some of them 

 eventually swim near the tips of archegonia. As the egg matures, the 

 interior row of cells (neck-canal cells) of each archegonium disinte- 

 grates into a mucilaginous mass from which sugars diffuse into the sm- 

 rounding water. When the sperms come in contact with the diffusing 

 sugar they may swim toward the archegonium where the sugar is most 

 concentrated. A few eventually pass into the neck of the archegonium, 

 and one may finally move all the way to the egg and fuse with it. The 

 fertilized egg, or zvgote, is the beginning of the sporophvte phase of the 

 moss plant. 



The sporophvte and asexual reproduction. The oospore germinates 

 while still within the archegonium at the apex of the leafy stem, and 

 from it develops a slender, stalk-like, leafless structure tenninating in a 

 capsule, or sporangium. In some mosses the stalk, or seta, is very short; 

 in others two to four inches in length. The capsule is usually simple, but 

 in some of the common mosses it is quite complex. In most species the 

 main body or urn of the sporangium is surmounted bv an easilv separable 



