GROUP I. THALLOPHYTA : ALG^ : GHLOBOPHTCEJI. 



253 



zellen) are cut off from the basal portion of the -oosphere by the formation of 

 cell-walls ; these cells are probably to be regarded as polar bodies. 



At the time of fertilisation, the cells of the crown separate so as to form a 

 channel leading to the apex of the oogonium. The wall of the oogonium is not 



FIG. 181. Charafragilis, reproductive organs (after Strasburger). A Median longitudinal 

 section through a leaf (gametophyll) r, and the sexual organs which it bears ; a antheri- 

 dium, borne on a nodal cell no, by the stalk-cell p ; m the manubria; ob an oogonium, 

 borne on a nodal cell no and an internodal stalk-cell po; v wendungszelle; c corona (all 

 x 90). B spermatozoids ( x 540). 



ruptured, but it becomes mucilaginous. The spermatozoids enter the channel 

 and reach the apex of the oogonium ; one of them makes its way through the 



