VASCULAR CRYPTOGAMS 17 



wertnost portion of the lowest cell remiins of a comparatively large 

 ze, and is the central cell containing the oosphere. When mature, the 

 vo canal-cells deliquesce into mucilage, which swells up considerably, 

 rives apart the four apical lid-cells or stigmatic cells of the neck, and 



ejected ; an open canal being thus formed, to allow the access of the 

 itherozoids to the oosphere, which always takes place in moisture, the 

 iected mucilage assisting also in this process. 



The antherids appear as roundish papillae on the margin, or dispersed 

 ver the under surface of the prothallium ; in some cases they are im- 

 edded in its tissue. Each antherid consists of a comparatively small 

 umber of cells ; when mature the cell-walls are ruptured under water, 

 iid from each escapes a swarming antherozoid. The antherozoids are 

 jirally coiled threads of protoplasm, the body of which is formed from 

 le nucleus of the mother-cell, with a number of fine vibratile cilia 

 n the anterior coils. There is generally attached to each anthero- 

 Did, as it escapes from its mother-cell, a vesicle of protoplasm contain- 

 ig starch-grains, formed out of the cytoplasm of the mother-cell, which, 

 ihering to one of its posterior coils, is dragged along with it during its 

 varming, but becomes detached before its entry into the neck of the 

 rchegone. In the heterospo'rous families the antherid is of very simple 

 Tucture, and is either produced directly within the microspore, or after 

 le preliminary formation of a few cells, which must be regarded as a 

 idimentary prothallium. 



The form and size of the non-sexual generation or sporophyte vary 

 ithin very wide limits, from the filmy, moss-like Hymenophyllacese 

 Filices) to the arborescent tree-ferns (Filices), and must be described 

 lore in detail under the various families. It arises in the archegone, 

 om the oosperm or fertilised oosphere. The first efTect of impregnation 



that the oosphere invests itself with a cell-wall of cellulose, thus 

 ecoming the oosperm, which then divides into a small number of 

 ndifferentiated cells, in which condition it is known as the embryo. In 

 le earliest subsequent divisions of the embryo may be recognised the 

 idiments of the first root, of the first leaf or cotyledon, and of the apex 

 f the stem ; while at the same time a lateral outgrowth termed the foot 



formed at the bottom of the venter, and draws from the prothallium 

 le first nourishment for the young plant. The venter at first grows 

 igorously, enveloping the embryo, until this latter finally protrudes 

 ee, leaving the foot still attached to it for some time as a nutritive 

 rgan. The primary root soon disappears, and in some Hymenophyl- 

 .cese, and in Salvinia and Psilotum, is not followed by others ; but in 

 le great majority of cases other true roots succeed in acropetal suc- 

 ;ssion, and the prothallium then disappears. The cotyledon always 



c 



