CRYPTOGAMS 201 



weed — and like the zoospores of many Algse — in hav- 

 ing two cilia for locomotion. 



467. The archegonial branches bear on the under side 

 at the base of the rays rows of flask-shaped organs called 

 arehego7iia (Fig. 334, b). In the archegonium an egg cell 

 (e) is situated at the center of the enlarged basal jjart. 

 When ready for fertilization the Qgg may be reached 

 through the canal in the slender portion, or neck, of the 

 archegonium. When the dew is on the plants the anthero- 

 zoids make their way to the archegonial branches (which 

 at the season of fertilization are not much grow^n), and 

 swarm to the mouth of the archegonia. One of them 

 passes through the canal and fuses with the Qgg cell. 



468. In most cases of oosporic reproduction in Algae 

 and Fungi, it will be remembered, the oospore falls from 

 the parent plant before it germinates. In Nemalion, 

 however, fertilization of the Qgg gives rise to a structure 

 organically united to the original plant ; this structure 

 ultimately bears spores (carpospores), serving to dis- 

 seminate the species. Marchantia is like Nemalion in 

 the noteworthy fact that the oospore gei^minates in posi- 

 tion^ and gives rise to spores 07ilg after an interval of 

 growth upon the parent playit. For after fertilization the 

 oospore divides into two, then into four, then into eight 

 parts, and so on. The mass of cells thus originating 

 grows and finally forms a stalked spore capsule (Fig. 

 334, c, d), or sporogonium. The foot of the sporogonium 

 is embedded in the tissue at the base of the old arche- 

 gonium (ar). 



469. The spores are numerous, free, rounded or some- 

 what angular, walled cells. When the capsule bursts, one 

 sees that it contains a great number of fine threads mixed 

 with the spores. They have the property of twisting and 

 untwisting with changes of atmospheric moisture, and so 

 serve to give the spores to the winds from time to time. 

 From the spores new plants develop. 



470. The archegonium is a structure that is found in 

 no plant lower than the Liverworts. As we go upward. 



