GROUPS OF PLANTS. 45 



which gives name to the group. The archegonium is a flask- 

 shaped cellular body consisting of a basal portion or venter, 

 which contains a single egg, and a neck through which the 

 sperms enter (Figs. 32, 34). 



In the life history of this group of plants there are two gen- 

 erations or phases of development. During one stage the arche- 

 gonium and antheridium are developed and this is known as the 

 sexual generation, and as these organs give rise to gametes or 

 sexual cells it is also spoken of as the gametophyte. By the union 

 of the sex cells (sperm and egg) an oospore is formed which 

 germinates at once within the archegonium. That portion of the 

 plant which develops from the oospore gives rise to asexual spores 

 and hence this phase is called the asexual generation. It is also 

 spoken of as the sporophyte from the fact that it gives rise to 

 spores. These spores are in the nature of resting spores and do 

 not germinate on the plant as does the oospore. They are dis- 

 tributed and on germination give rise to the gametophyte stage. 



In some of the Archegoniates these two phases are combined 

 in one plant as in the Bryophytes, whereas in other members of 

 the group the two phases are represented by two distinct plants, 

 that is, the gametophyte and sporophyte become independent of 

 each other, as in the Ferns. 



The following table shows the main divisions and subdivisions 

 of the Archegoniates: 



Archegoniates 



Bryophytes jHepaticse (Liverworts) 



iMusci (Mosses). 



fFilicales (Ferns). 

 iPteridophytes. . . Equisetales (Horsetails). 



ILycopodiales (Club Mosses). 



BRYOPHYTES. 



The structure of the sexual organs in the Liverworts (Fig. 27) 

 and Mosses (Fig. 32) is essentially the same, but the vegetative 

 organs are more or less dissimilar. In the Liverworts the plant 



