338 



DEVELOPMENT OF SPORES. 



PART II. 



and sidewise ; it is placed at a little distance from the 

 antheridia, and after being fertilized by the active fila- 

 ments or spermatozoids, and matured, it contains the 

 primordial cell of the young fern, which soon sends 

 forth leaves rolled up and curled inwards previous to 



Fig. 52. Antheridium and Spermatozoids of Pteris serrulata : A, projection of one of the 

 cells of the prothallus showing the antheridial cell (b) ; B, antheridiumjfully developed, 

 containing sperm-cells, each enclosing a spermatozoid ; c, one of the spermatozoids 

 magnified, showing the cilia. 



expansion, and a root, which being sufficient to feed 

 the plant, the flat pro-embryo, which was the first 

 stage of development, perishes. Thus in the family of 

 ferns there are two distinct periods of growth, and one 



Fig. 53. Archegonium of Pteris serrulata : A, as seen from above ; B, side view, show- 

 ing at A the cavity containing the germ cell ; at B, the walls of the archegonium 

 made up of four layers of cells ; and at c, the spermatozoids within the cavity. 



only of fertilization. In flowering plants, fertilization 

 and its products are the final result of vegetation, and 

 the maturation of the fructification is frequently fol- 

 lowed by death. In the ferns, on the contrary, fertilization 

 precedes the development of the plant, which, if peren- 

 nial, continues to bear fertilized fruit year after year. 



