STUDIES IN CRYPTOGAMS 



197 



is always conspicuously notched. There is a prominent midrib 

 extending along the center of each branch of the thallus. On the 

 under side of the thallus, especially along the midrib, there are 

 numerous rhizoids which serve the purpose of roots ; absorbing 

 nourishment from the earth and 

 holding the plant in its place. The 

 upper surface of the thallus is di- 

 vided into minute rhombic areas 

 that can be seen with the naked 

 eye. Each of these areas is per- 

 forated by a small breathing pore 

 or stomate that leads into a cavity 

 just beneath the epidermis. This 

 space is surrounded by chlorophyll- 

 bearing cells, some of which stand 

 in rows from the bottom of the 

 cavity (Fig. 290). 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 containing 

 small green bodies. These bodies are buds or gemma 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. 288, 289. These are 

 termed archegoniophores and antheridiophores or receptacles. Their 

 structure and function are very interesting, but their parts are so 

 minute that they can be studied only with the aid of a microscope 

 magnifying from 100 to 400 times. Enlarged drawings will guide 

 the pupil. 



Fig. 290. — Section of Thallus 

 OF Marchantia. Stomate at a. 



Fig. 291. — Section through Antheriiuophore of Marchantia, 

 showing antheridia. One antheridium more magnified. 



The antheridiophores are fleshy, lobed disks borne on short stalks 

 (Fig. 291 ). The upper surface of the disk shows openings scarcely 

 visible to the naked eye. However, a section of the disk, such as 

 is drawn in Fig. 291, shows that the pores lead into oblong cavi- 



