276 



THE BRYOPHYTES 



283. The Sexual organs. The sexual organs of the bryophytes 

 are many-celled. They are male and female and each consists 

 of a cellular case, or capsule, in which 

 are formed the respective gametes, which 

 are sperms and eggs. It will be remem- 

 bered that the sexual organs of the thal- 

 lophytes are, with very few exceptions, 

 one-celled. The conspicuous exceptions 

 are the plurilocular sexual organs of the 

 lower brown algae (see Ectocarpus, Sec. 

 235) and the antheridium of the stone- 

 worts (Sec. 230). 



The sperm-producing organ, or anther- 

 idium. The antheridium (Fig. 243) is a 

 stalked, oval or elliptical structure, with 

 an outer cellular envelope inclosing a 

 dense mass of very small cubical cells 

 in which are developed the sperms. The 

 sperms are minute elongated or slightly 

 coiled protoplasts, with a pair of cilia at 

 one end. The mature antheridia only dis- 

 charge their sperms when wet, as after 

 heavy rains or dews, and the sperms then 

 FIG. 244. The a r die go- swim about in the moisture. At these 

 nium of a liverwort times the plants are practically leading 

 an aquatic life like their algal ancestors, 

 Thearchegoniainthisgenus d ^ development of motile sperms 



hang down from a special r 



receptacle (Fig. 251). The in these land plants shows clearly that 

 rjL ta i 7. they must have come from forms with 



archegonium, while the aquatic life habits. 



^"cT^l 1 ^ Th* egg-prodncint, organ, or archego- 

 down into mucilage as the nium. The female organ is called an 



archegonium matures. archeg onium. It IS flask-shaped (Fig. 244), 



and the outer cellular envelope incloses at maturity a row of cells. 

 The cell situated in the enlarged portion of the archegonium 



