366 MOSSES 



top of the stems. Some mosses have both antheridia and 

 archegonia on the same plant, while other mosses have 

 only one kind on each plant. The moss plant which 

 bears the antheridia is usually short and has on the top 

 a rosette of leaves, in the center of which is the sex 

 organ. 



Many sperms come from each of the antheridia, which 

 move by the use of cilia when water is present, a film of 

 dew being sufficient. The female moss plant has on its 

 upper end one or more archegonia, each of which contains 

 an egg cell. When the egg is ripe or ready to be ferti- 

 lized, sperms may swim to it if water is present. A 

 sperm enters the archegonium and fuses with the egg cell, 

 thus forming a sexual cell, known as the fertilized egg 

 cell. 



From this fertilized egg cell a sporophyte (spore plant) 

 grows out of the archegonium. The sporophyte consists 

 of a foot, a pad by which it gets its food from the gameto- 

 phyte, the seta, a slender stalk, and the capsule or spore- 

 case. While every mature gametophyte leads an inde- 

 pendent existence, the sporophyte is a parasite. 



Thus in its life history the moss plant has two distinct 

 generations, the gametophyte or sexual and the sporophyte 

 which reproduces asexually (Figure 390). 



258. Economic Value. — Mosses have little economic 

 value, except in cold regions where some kinds are dug 

 from under the snow for food for the reindeer. They are 

 interesting as showing a stage of development of the 

 higher plants. 



LABORATORY STUDY 



Moss (Polytrichum). Study moss plants and note the difference in 

 size between the male and female plants. Make a drawing to show the 

 difference in size and in the arrangement of the leaves. Select a female 

 gametophyte which has a sporophyte. Draw and label the seta or stalk, 



