MOSSES 355 



sexual organs, the leafy-stemmed plant of the foliose liverworts, 

 the protonema and leafy-stemmed moss plant, is the gamete 

 plant stage (gametophyte). Each one of these stages begins and 

 ends with a single cell. The gamete plant begins with the spore 

 and ends with the unfertilized egg in the egg case. The spore 

 plant begins with the fertilized egg and ends with the mother 

 cell (of the spores) in the capsule. 



Sporophyte 



Diagram No. IV. Illustrating the life cycle of the Bryophytes (a liverwort or moss.) 

 Course of development follows the direction indicated by arrows. The zygote is the fertil- 

 ized egg. Vegetative multiplication by buds and filamentous outgrowths of the thallus. 

 Note increase of sporophyte. 



508. Comparative review of the mosses. The first genera- 

 tion (or gametophyte) of the mosses begins with the spore which 

 produces the protonema, either a branched filamentous green 

 growth, or a thallose one as in the peat mosses. This suggests 

 that the ancestors of the mosses were plants resembling the 

 algce or liverworts, though no alga or liverwort is now known 

 which could be regarded as an ancestor of the mosses. From 

 the protonema the leafy-stemmed moss plant is developed as a 

 branch. This bears the sexual organs. The second generation 

 (or sporophyte) is developed from the fertilized egg. It remains 

 dependent on the leafy stemmed plant for its food, the stalk being 

 wedged into the tissues of the stem. The capsule of the mosses 

 is a much more highly developed and complex structure than 



