BEYOPHYTES 



305 



globular body (Figs. 277, 278). A section through this 



body shows it to consist of a single layer of cells, which 



forms the wall of the antheridium, and 



within this a compact mass of small 



cubical (square in section) cells, within 



each one of which there is formed a 



single sperm (Fig. 278). The sperm is 



a very small cell with two long cilia 



(Fig. 277). These small biciliate sperms 



are one of the distinguishing marks 



of the Bryophytes. When the mature 



antheridia are wet they are opened at 



the apex and discharge their contents 



(Fig. 277), and the sperms escaping 



swim actively about. 



199. The archegonium. — This name 

 is given to the female sex organ, which 

 is a many-celled structure, shaped like 

 a flask (Figs. 277, 287). The neck of 

 the flask is more or less elongated, and 

 within the bulbous base (venter) the single egg is organized. 



To this neck the swimming sperms are attracted, enter 

 and pass down it, one of them fuses with the egg, and this 

 act of fertilization results in an oospore. 



200. Germination of the oospore. — The oospore in Bryo- 

 phytes is not a resting spore, but germinates immediately 

 by cell division, forming the sporophyte embryo, which 

 presently develops into the mature sporophyte (Fig. 279, A). 

 The lower part of the embryo develops the foot, which 

 obtains a firm anchorage in the gametophore by the latter 

 growing up around it (Fig. 279, B, C). The upper part of 

 the embryo develops upward, organizing the seta and cap- 

 sule. As the embryo increases in size, the venter of the 

 archegonium grows also, forming what is called the calyptra; 

 and in true mosses the embryo presently breaks loose the 

 calyptra at its base and carries it upward perched on the top 



Fig. 278. Antheridium of 

 a liverwort in section, 

 showing single layer 

 of wall cells surround- 

 ing the mass of moth- 

 er cells. — After Stras- 



BDRGER. 



