400 



THE NON-VASCULAR PLANTS 



cilia. They are so small that a film of dew is quite enough 

 for them to swim in, and when the sperms of Marchantia 

 are discharged from the antheridia, there is nearly always 

 enough moisture on the surface of the 

 plant to permit them to swim to the 

 archegonia. To reach the eggs they 

 have to swim up, but at the time 

 when swimming occurs the stalks of 

 the archegoniophores are quite short ; 

 not nearly so long as they become 

 later. Most of the liverworts do not 

 bear their archegonia upon stalked 

 organs, and of course in such cases 

 the journey of the sperms to the eggs 

 is much simpler than in Marchantia. 

 What happens after fertihzation is 

 particularly important for you to 

 note. You remember that in (Edo- 

 gonium the fertilized egg or oospore 

 does not grow directly into a plant 

 like its parent; it divides into four spores, and each of 

 these is capable of producing a new plant. In liverworts 

 we find this process carried still further. We find "the 

 oospore not only forming a number of spores; we find it 

 growing into a special organ many of whose cells are not 

 spores at all. This organ is called a sporogonium. (See 

 Figure 198.) The sporogonium in Marchantia is an organ 

 big enough to be seen easily by the naked eye. It contains 

 spores, but it also contains many cells of other kinds. Be- 

 sides the cells of the wall and the foot and the seta, there are 

 the elaters, peculiar spirally-marked cells which appear 

 among the spores and, by twisting as they dry, push the 



Fig. IQ7'. "^ A young an- 

 theridium of Marchantia. 

 Also two of the biciliate 

 sperms from a ripe an- 

 theridium. 



