Sexual reproduction 391 



division the apical cap is detached and through the aperture is protruded a 

 more or less cylindrical outgrowth clothed in a cellulose wall. This is the 

 second cell of the now bicellular plant which either pushes the cap on one 

 side like a hinged lid (fig. 246 G) or carries it upwards on its apex (fig. 246 F 

 and H). This type of growth is the result of the new substance of the cell- 

 wall not arising in the form of a ring but as a hemispherical layer in the 

 upper part of the rounded basal cell. 



H 



Fig. 245. A, three generations of (Edogonium rivulare (L. 01.) A. Br., two unicellular plants and 

 an escaping zoogonidiura (z), x 310. BH, (E. fonticola A. Br., x 330. B, female plant 

 with two oogonia containing oospores (os) and two androzoogonidangia (az) each containing 

 a single immature androzoogonidium ; C and D, young male plants which were attached ; 

 E H, developing androzoogonidia which were unattached, showing the much-branched 

 basal disc. 



In the first type of germination the actual attachment of the basal cell to the sub- 

 stratum appears to be by a brown cementing substance which is either ferric oxide or 

 some ferric salt (Fritsch, '02), but in the second type of germination there is evidence that 

 the depressed basal cell is attached by a tough mucus. 



Sexual reproduction in the (Edogoniales is of a high type and there is a 

 greater specialization of the male and female organs than in any other Green 

 Algae. The sexual organs are oogonia and antheridia. The oogonium arises 

 as a result of the division of a vegetative cell, and in (Edogonium the lower 

 cell forms a supporting cell while the upper cell becomes the oogonium. This 



