REPRODUCTION IN PLANTS 



259 



divisions to form a large number of haploid spores. The ripe spores, when 

 discharged from the capsule, may fall nearby or be carried a considerable 

 distance by the wind. Those that chance to alight in a favorable en- 

 vironment absorb water and germinate to produce new gametophyte 

 individuals. 



marginal sori with sporangia 



portion of 

 leaf of 

 sporophyte 

 generation 



spore 



\^J sporangia 

 | with 

 • spores 



young gametophyte 

 produced by 

 germinating spore 



prothallus- 



gametophyte 



plant 



(prothallus) 



^orchegonia 



. antheridia 



young sporophyte 1 



Fia. 17.5. Alternation of generations in the Pteridophyta. The life cycle of a fern. (Modified 

 from Turtox chart, courtesy General Biological Supply House, Inc.) 



THE ALTERNATION OF GENERATIONS IN THE PTERIDOPHYTES 



In the ferns — and their relatives, the club mosses and horsetails — we 

 find the most striking alternation of generations that occurs among 

 plants. It is now the sporophyte generation that is the more accentuated 

 and conspicuous, so that the plants we recognize as ferns, club mosses, 

 or horsetails are members of the sporophyte generation. The gameto- 

 phyte generation is reduced to small but free-living plants that persist 

 only long enough to give rise to a new sporophyte generation. 



