THE LIVERWORTS OR HEPATICS 



517 



Fig. 340, III. — Umbrella-liverwort. Antheridium (V) showing the numer- 

 ous cells within which produce spermatozoids. (Atkinson.) 



Fig. 340, IV. — Umbrella-liverwort. Spermatozoids, highly magnified. 

 (Atkinson.) 



expansion (Fig. 341, I-V), but they come finally to lie underneath 

 through the folding downward of the edges of the lobes. The 

 female gametangia are thus protected by their position, and besides 

 this they are covered by a hanging curtain (Fig. 3-41, V, p). When 

 the plants are wet with rain or dew the flagellate male gametes are 

 set free and swim or crawl from their elevated home down the 

 stalk and to a female plant ; then they climb up its stalk (doubtless 

 aided by numerous hairs thereon) to the archegonia. The fer- 

 tilized egg-cell gives rise to a spheroidal embryo which develops 

 into a sporophyte resembling that of Riccia for a while but finally, 

 by growth of the basal region of the capsule, producing a foot- 

 stalk whose elongation pushes the sporangium through the top 

 of the calyptra (Fig. 341, III). Meanwhile, elongated cells, 

 called elaters i (Fig. 341, IV), having elastic, spirally thickened 

 walls are being formed among the spores; and when finally the cap- 

 sule bursts open these elaters, by mechanical movements due to 

 drying, eject the spores and so help to scatter them. The sporo- 

 phyte is fed entirely by the gametophyte and lives as a parasite, the 

 foot or lower end of the stalk serving as an haustorium. 



Especial interest attaches to the genus Anthoceros (often called 

 horned liverworts from the form of the sporophyte), because these 

 humble plants have preserved structures which help us to under- 

 stand how all the higher plants may have originated. The game- 



1 E-la'ter < Gr. elaler, a driver. 



