LIVERWORTS 



187 



branch of the thallus. On the under side of the thallus, especially 

 along the midrib, there are numerous rhizoids which serve the pur- 

 pose of roots, absorbing nourishment from the earth and holding the 

 plant in its place. The upper surface of the thallus is divided into 

 minute rhombic areas which can be seen with the naked eye. Each 

 of these areas is perforated by a small breathing pore or stomate which 



331. 



Plants of marchantia. 



332. 



leads into a cavity just beneath the epidermis. This space is sur- 

 rounded by chlorophyll-bearing cells, some of which stand in rows 

 from the bottom of the cavity (Fig. 333). The delicate assimilating 

 tissue is thus brought in close communication with the outer air 

 through the pore in the thick protecting epidermis. 



At various points on the midrib are little cups which contain 

 small green bodies. These bodies are buds or gemmce which are 

 outgrowths from the cells at the bottom of the cup. They become 

 loosened and are then dispersed by the rain to other places where 

 they take root and grow into new 

 plants. 



The most striking organs on the 

 thallus of marchantia are the peculiar 

 stalked bodies shown in Figs. 331, 

 332. These are termed archegonio- 

 phores and antheridiophores or recepta- 

 cles. Their structure and function are 

 very interesting, but their parts are so 

 minute that they can be studied only 333. Section of thallus of marchantia. 

 with the aid of a microscope magnify- Stomate at a. 



ing from 100 to 400 times. Enlarged drawings will guide the pupil. 



The antheridiophores are fleshy lobed disks borne on short stalks 

 (Fig. 331). The upper surface of the disk shows openings scarcely 



