126 ELEMENTS OF BIOLOGY. 



similar element. These spores give rise to a temporary 

 organism, the sole function of which is to develop the 

 special organs in which the essential elements of reproduc- 

 tion may be produced. The contact of these elements gives 

 rise to an embryo, which is developed into the original 

 " sporangiferous " frond by which the spores were pro- 

 duced, and not into the temporary cellular expansion on 

 which the generative elements were carried. There is thus 

 an alternation of gemmation with generation, the generative 

 process being carried on by a minute provisional organism, 

 developed by budding from a conspicuous leafy frond, 

 which latter is produced in a true sexual manner. 



