MOSSES 325 



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. 



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. 



493. 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 

 algae 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 

 that of the liverworts, and shows that the mosses stand higher in 

 the scale of classification and development than the liverworts. 



494. Relationship of the liverworts and mosses. There 

 are, however, taken as a whole, very close relationships between 

 the liverworts and mosses, shown in the character of the sexual 

 organs, and especially in the capsule, though there are great 



