THE TWO GENERATIONS 



411 



foot extends into the gametophore and absorbs food which is 

 supplied to the elongating stalk and developing sporangium. 

 In the sporangium are produced numerous spores and also 

 elongated twisted cells called elaters, which assist in scattering 

 the spores. When the spores are 

 mature the sporangial wall opens 

 and the spores are scattered. When 

 the spores fall on a moist substra- 

 tum, they germinate and produce 

 new thallus plants like the ones 

 described. 



The Two Generations. The ob- 

 long body produced by the fertilized 

 egg, and consisting of foot, stalk, 

 and sporangium, is regarded as a 

 plant within itself. When fully 

 mature it is so small that one must 

 look closely under the finger-like 

 lobes to find it. It doesn't look 

 much like a plant, since it is so 

 simple and depends upon the 

 gametophore for food and water, 

 but it is this plant that differenti- 

 ates and becomes the conspicuous 



plant body of the higher plants. Since it produces spores, it 

 is called a spore plant or sporophyte. When one is reminded 

 that a Corn plant or Apple tree is all sporophyte excepting some 

 microscopical structures within the flowers, then the significance 

 of this small sporophyte of the Liverworts in relation to the 

 origin of the higher plants may be realized. 



It is obvious that if this little sporophyte is regarded as a plant, 

 then all of the remainder of Marchantia must be regarded as 

 another plant. This other plant consists of all that has been 

 described as the plant body of Marchantia. It consists of the 

 flat prostrate thallus and the gametophores with the sex organs 

 and gametes. Since it is the function of this plant to bear 

 gametes, it is called gametophyte. 



It follows then that the complete life cycle of Marchantia in- 

 volves two plants or generations as illustrated in Figure 867. 

 The gametophyte generation develops from a spore and produces 



FIG. 366. Highly magnified 

 vertical section through the 

 expanded top or/ionceptacle of 

 a male gametophore, showing 

 the antheridia (a) imbedded in 

 the gametophore and consist- 

 ing of a short stalk and of a 

 jacket enclosing numerous cells 

 which form sperms. 



