186 



ELEMENTS 01* <( W*CTt T RAL BOTANY. 



of tissue in which are developed cells corresponding to ths 

 pollen-grains of phanerogams. These projections are the 

 antheridia; they contain ceHs in wh?ch are fertilizing bodies 

 known as antherozoids. Also on the under suiface of the 



prothallium, near the notch, 

 we find structures analogous 

 to the embryo-sac of the 

 phanerogamous ovule. These 

 are the archegonia. They 

 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 IrVe *fre one which 

 originally bore the spores on its fronds. 



326. It is manifest, then, that we have here 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 boars the 

 spores. This phenomenon is spoken of as the alternation 

 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 a Fern, under side ; h, root-haira ; an, antheridia} 

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



