Lecture XVIL 



129 



to the base of the cavity by a slender stalk. The antheridium is 

 a thin-walled sac containing countless sperm-cells. When the 

 sperms are ripe, if water finds its way to the upper surface of the 

 antheridiophore it is drawn through the narrow canal, and passing 

 into the cavity leads to the rupture of the antheridium. The 

 sperms are discharged as a milky droplet and are driven out on 

 the surface of the antheridiophore. They are threadlike and very 



FIG. 24. Marchantia polymorpha, longitudinal section of antheridiophore 

 on left and of archegoniophore on right, x 25. a, young antheridium 

 cut in median plane; b, outside of young antheridium; t, antheridial 

 cavity showing the cells which line it ; d, median section of older antherid- 

 ium ; e, ventilating pore ; /, photosynthetic filaments ; g, membrane 

 surrounding archegonia; h and i, archegonia ; k, rhizoids in one of the 

 longitudinal grooves of the stalk ; s, scale on antheridiophore. (Partly 

 after Kny.) 



minute ; they possess two long cilia. While still in the antheridium 

 the sperms appear as a ring or flattened spiral, but when they are 

 set free they assume the shape of a cork-screw blade. They are 

 carried by dew or rain falling on the upper surface of the antheri- 

 diophore over its margin and are, in all probability, conducted to 

 the soil by rhizoids which are attached to the under surface of 

 the disc, and travel down the stalk by the two tubular channels 

 already mentioned. 



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