100 



PLANT STRUCTURES 



globular body (Figs. 83, 84, 103). 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 com- 

 pact mass of small cubical (square in section) cells, within 

 each one of which there is formed a single sperm (Fig. 84). 

 These cubical cells are evidently moth- 

 er cells, and to distinguish them from 

 others they are called sperm mother cells. 

 An antheridium, therefore, aside from 

 its stalk, is a mass of sperm mother 

 cells surrounded by a wall consisting 

 of one layer of cells. 



The sperm is a very small cell with 

 two long cilia (Fig. 83). The two 

 parts are spoken of as "body" and 

 cilia, and the body may be straight or 

 somewhat curved. These small bicili- 

 ate sperms are one of the distinguish- 

 ing marks of the Bryophytes. The 

 existence of male gametes in the form 

 of ciliated sperms indicates that fertil- 

 ization can take place only in the pres- 

 ence of water, so that while the plant 

 has become terrestrial, and its asexual spores have respond- 

 ed to the new conditions and are no longer ciliated, its 

 sexual process is conducted as among the Green Algae. It 

 must not be supposed, however, that any great amount of 

 water is necessary to enable sperms to swim, even a film 

 of dew often answering the purpose. 



When the mature antheridia are wet they are ruptured 

 at the apex and discharge the mother cells in ;i mass (Figs. 

 83, 105, E), the walls of the mother cells become mucilagi- 

 nous, and the sperms escaping swim actively about and are 

 attracted to the organ containing the egg. 



64. The archegonium. — This name is given to the female 

 sex organ, and it is very different from the oogonium of 



Fig. 84. Antheridium of 

 a liverwort in section, 

 Bhowing single layer 

 of wall cells surround- 

 ing the mass of moth- 

 er cells. — After Stras- 



EUBGER. 



