LIVERWORTS 



173 



of small, often crowded leaves (Fig. 168, B). There are 

 really three rows of leaves, but the third is against the 

 substratum and is usually so much changed in appearance 

 as not to resemble the other rows. 



There is, of co.urse, the same alternation of generations as 

 in the Marchantia forms, but the sporophyte is more than 

 a spore-case. It develops a distinct stalk or stem that 

 bears a spore-case at its summit, and therefore the sporo- 

 phyte has become more complex. Besides, the spore-case 

 does not burst open somewhat irregularly, as in the Mar- 

 chantia forms, but splits into four pieces that spread apart 

 and expose the spores. 



99. Anthoceros forms. This group contains compara- 

 tively few forms; but they are of great interest, since many 

 suppose that they are the liverworts that approach most 

 nearly the higher plants. The 

 thallus body is very simple, not 

 becoming so thick as are the 

 Marchantia bodies, nor becoming 

 leafy bodies as are those of the 

 leafy liverworts. 



The important feature of the 

 group is the sporophyte. At the 

 "fruiting" period the thallus be- 

 comes more or less covered by 

 structures that look like small, 

 erect grass-blades (Fig. 169). 

 Each of these blade-like bodies 

 is a sporophyte that has devel- 

 oped from an oospore lying ^ m 

 within an archegonium. The sporophyte has a large 

 bulbous base embedded in the simple thallus, and above 

 this base there arises a long pod-like spore-case. The 

 cells forming the wall of this spore-case contain chloro- 

 plasts, so that the sporophyte is able to make food for itself, 



FIG. 1 69. A rdhoce- 

 ros: A , thallus with 

 spore - cases (spor- 

 ophytes); B, a sin- 

 gle spore-case, hav- 

 ing split for the dis- 

 charge of spores. 



