The New Student's Reference Work/Alternation of Generations
Alterna'tion of Genera'tions. In all plant groups above the Thallophytes, the life history of every plant is made up of two phases. One phase bears the sex organs, and is called the gametophyte; the other bears no sex organs, but produces asexual spores, and is called the sporophyte. These two phases or generations regularly alternate with each other, the gametophyte by means of its sex organs producing the sporophyte, and the sporophyte by means of its asexual spores producing the gametophyte. For example, in the mosses the ordinary leafy plant is the gametophyte, and the so-called fruit is the sporophyte. In the ferns the leafy plant is the sporophyte, while the gametophyte is a very small but independent body, which is never observed except by those who know of its presence. In the flowering plants the whole visible body is the sporophyte; while the gametophyte is so minute that it is effectually concealed from ordinary observation. For a further account see Gametophyte and Sporophyte.