FIG. 213. Prothallium (gametophyte) of Aspidium. The under surface, as viewed 

 through a microscope. The necks of eight archegonia are indicated just below 

 the notch of the heart. The hair-like outgrowths are rhizoids. At the base of the 

 prothallium, among the rhizoids and to the right of them, numerous antheridia 

 are indicated. 



FIG. 214. Archegonia of a fern, showing the manner of development. At the 

 right is an archegonium ready for fertilization. From its neck is excreted a sub- 

 stance which attracts to it the swimming sperms which come near. 



(421) 



