182 A TEXT-BOOK OF BOTANY 



and the best exposure is not obtained. The mosses have 

 made still further progress in developing an erect branch 

 upon which leaves are spread out to the light and air freely 

 in all directions. All this advance has been made by the 

 gametophyte, which in the mosses has reached the best 

 position for leaves and hence for food manufacture. How 

 progress in this direction is carried further by the higher 

 plants will be seen in subsequent chapters. 



