214 



REPRODUCTION 



a very early period of its develogment, d, we find the sporangium 

 composed of a protoderm and a central cell. The protoderm 

 proceeds to the formation of an epidermis or sporangium wall, 



Mature tapetum of 

 two cell-layers 



Epidermis or 

 sporangium wall 



Archesporial cell 





of immature tapetum 



"- : 1 Immature grandmother-cells 



Tapetal plasmodium 

 formed by fusion of 

 tapetal pn ^^ ..^ ^^ ... ,, j^^^.. _ ^^^ ( / Mother ceUs have dlvided 



to form four spores only 

 three shown 



Grandmother-cell has divided 

 producing two mother-cells 



FIG. 122. Sporangium and spore formation of a fern, Aneimia Phyllitidis. a, growing 

 apex; i, group of three protodermal cells which are to give rise to a sporangium; b, c, d, e, 

 f, g, h, successive stages in sporangium and spore formation. Partly diagrammatic. 

 Further description in the text. 



