186 



ELEMENTS OF STEUCTURAL BOTANY.- 



of tissue in which are developed cells corresponding to the 

 pollen-grains of phanerogams. These projections are the 

 antheridia; they contain cells in which are fertilizing bodies 

 known as antherozoids. Also on the under surface of the 



prothallium, near the notch, 

 we find structures analogous 

 to the embryo-sac of the 

 phanerogamous ovule. These 

 are the archegonia. Thej^ 

 are mostly flask-shaped bod- 

 ies, having a germ-cell — the 

 oosphere — in the lower end. 

 The antherozoids, on escap- 

 ing from the antheridia, 

 make their way down the 

 necks of the archegonia, and 

 coming in contact .with the 

 oospheres fertilize them. As a result of this fertilization, 

 a plant is developed in all respects like the one which 

 originally bore the spores on its fronds. 



326. It is manifest, then, that we have^lere two distinct 

 generations : first, the spore produces the prothallium 

 which bears the antheridia and archegonia ; secondly, the 

 interaction of these gives rise to a plant which bears the 

 spores. This phenomenon is spoken of as the aMemation 

 of generations. 



327. The stems and roots of Ferns are found to contain 

 vascular bundles which, like those of monocotyledons, are 

 closed. 



Fig. 235. 



Fig. 235. — Prothallium of p, Fern, under side ; A, root-Iiairs ; an. antlieridia; 

 ar, archegonia. Magnified 10 times. (Prantl.) 



