182 STRUCTURE AND LIFE HISTORIES 



gametophyte, on the other hand, being derived from a sin- 

 gle reproductive cell (the spore) , without nuclear or cell-fu- 

 sions, is composed of cells of a single or haploid nature. 



166. Alternation of Generations. Our study of the 

 fern also brought out another fact of very fundamental 

 importance. Sporophytes do not produce sporophytes, 

 nor gametophytes, gametophytes; but there is always 

 an alternation of generations, sporophytes producing 

 gametophytes, and gametophytes, sporophytes. 



The order of sequence in the life-cycle is as follows: 



sporophyte >spore ^gametophyte >gametes o6sperm sporophyte. 



The order of structures and processes involved in the 

 life-cycle is as follows: 



OUTLINE OF LIFE HISTORY OF A FERN 



Gametophyte (prothallus) 



Antheridium Archegonium 



4 4- 



Sperm (male gamete) Egg (female gamete) 



Fertilization 



^ ^ 



Oosperm (zygote) 



44. 



Embryo 



-U 



Mature sporophyte (mature zygote) 



4-4- 



Sporophyll 



4- J' 



Sporangium 

 Spore-mother-cell 



I 1 I I ) 



Spore Spore Spore Spore 

 Gametophyte 



Reduction 



