EXAMINATION OF A MOSS. 



193 



stem with several archegonia in the centre, and Fig. 243 

 shows a single archegonium very highly magnified. The 

 antherozoids upon being set free 

 make their way down the necks 

 of the archegonia, and unite 

 their substance with that of 

 special cells in the lower end 

 (one in each archegonium). These 

 cells, as a consequence of being 

 thus fertilized, become sur- 

 rounded by a thin coat and 

 immediately begin to grow up- 

 wards, developing the slender 

 stalks (setae) with the capsules 

 at the summit, and surmounted 

 by the calyptra, which is, in 

 fact, nothing but the wall of the 

 archegonium which is torn away 

 at its base and carried upwards. Then the 

 spores are developed around the columella, 

 and the round of life of the plant is com- 

 pleted. 



As in the Ferns, we have here also 

 exhibited an alternation of generations, the 

 one generation being that arising from the 

 development of the spore and resulting in 

 the production of the antheridia and the archegonia ; the 

 other being that arising from the fertilization of the 



Fig. 242. Enlarged view of apex of the fertile stem of a Moss; a, archegonia; 

 6, leaves. 



Fig. 213. Very highly magnified view of an archegonium ; b, the base ; 

 h, the neck ; m, the mouth ; the germ-cell is seen at the bottom of the flask- 

 shaped cavity. (Sachs.) 



Fig. 243. 



