FEXNS. 



173 



come near the neck, and here they are caught in the viscid 

 substance which has oozed out of the canal of the archegonium. 

 From here they slowly swim down the canal, and finally one 

 sinks into the egg, fuses with the nucleus of the latter, and the 

 egg is then fertilized. It is now ready to grow and develop into 

 the fern plant. This brings us back to the sporophyte, which 

 begins with the fertilized egg. 



Synopsis. 



Sexual stage. 



Prothallium. 



(Corresponds to the 

 vegetative part 

 of the liverwort 

 and moss.) 



Flattened, green, heart-shaped growth, with rhizoids 

 underneath. 



Sexual organs, under side of prothallium. 



Antheridium. 



( Wall. 



( Sperm atozoids. 



Archegonium. j WalL 

 1 Egg- 



Material and apparatus. Prothallia of ferns, entire ; they are often found 

 growing in soil of pots in greenhouses where ferns are grown. Or they 

 may be grown by sowing the spores. 



For demonstrations of the structure of the sexual organs the teacher can 

 make sections, or permanent ones may be obtained from supply companies. 



Apparatus, same as in Chapter XXIV. 



