198 



PL AM' BIOLOGY 



Flu. 292. 



ARCHEGO- 



NIUM OK 



MARCHANTIA. 



ties in the receptacle. From the base of each cavity there arises 

 a thick, club-shaped body, the antheridium. Within the anther- 

 idium are formed many sperm -cells which are capa- 

 ble of swimming about in water by means of long 

 lashes or cilia attached to them. When the anther- 

 idium is mature, it bursts and allows the ciliated 

 sperm cells to escape. 



The archegoniophores are also elevated on stalks 

 (Fig. 289). Instead of a simple disk, the recepta- 

 cle consists of nine or more finger-like rays. Along 

 the under side of the rays, between delicately 

 fringed curtains, peculiar flask-like bodies, or arche- 

 gonia, are situated. The archegonia are not visible 

 to the naked eye. They can be studied only with 

 the microscope (x about 400). One of them 

 much magnified is represented in Fig. 292. Its 

 principal parts are the long neck, a, and the 

 rounded venter, b, inclosing a large free cell the 

 egg-cell. 



We have seen that the antheridium at maturity discharges its 

 sperm-cells. These swim about in the water provided by the dew 

 and rain. Some of them finally find their way 

 to the archegonia and egg-cells, the latter 

 being fertilized, as pollen fertilizes the ovules 

 of higher plants. 



After fertilization the egg-cell develops into 

 the spore capsule or sporogonium. The mature 

 spore capsules may be seen in Fig. 293. They 

 consist of an oval spore-case on a short stalk, 

 the base of which is imbedded in the tissue of 

 the receptacle, from which it derives the neces- 

 sary nourishment for the development of the 

 sporogonium. At maturity the sporogonium 

 is ruptured at the apex, setting free the spheri- 

 cal spores together with numerous filaments 

 having spirally thickened walls (Fig. 294). These filaments are 

 called elaters. When drying, they exhibit rapid movements by 

 means of which the spores are scattered. The spores germinate 

 and again produce the thallus of marchantia. 



FIG. 293. ARCHE- 

 GONIOPHORE, 

 WITH SPORO- 

 GONIA, OF MAR- 

 CHANTIA. 



FIG. 294. SPORES AND ELATERS OF MARCHANTIA. 



