EUPHYCOPHYTA 119 



Antheridia. Fig. 68 



The apical cell of the lateral branch cuts off one or two discoid 

 cells at the base and then becomes spherical. The upper spherical 

 cell divides into octants and this is followed by two periclinal divi- 

 sions after which the whole enlarges and the eight peripheral cells 

 develop carved plates (shields), thus giving the wall a pseudo- 

 cellular appearance. At maturity these peripheral cells acquire bril- 

 liant orange contents. The uppermost discoid basal cell protrudes 

 somewhat into the hollow structure formed as described above. 

 The middle segment of each primary diagonal cell now develops 

 into a rod-shaped structure, the manubrium, which bears at its 

 distal end one or more small cells, the capitula; every one of these 

 produces six secondary capitula from each of which arises a forked 

 spermatogenous thread containing 100-200 cells. These antheridial 

 cells each produce one antherozoid, an elongate body with two 

 flagella situated just behind the apex. The complete structure has 

 been regarded as one antheridiimi, whilst another view regards the 

 octants as laterals, the manubriimi as an internode, the capitula as 

 a node and the spermatogenous threads as modified laterals, so that 

 on this basis the antheridia are one-celled and conform to the 

 normal structure of the majority of the antheridia in the green algae. 

 This second interpretation, if it is correct, helps considerably in 

 understanding this pecuHar group. 



Oogonia. Fig. 69 



The apical cell of the lateral branch divides twice giving rise to 

 a row of three cells, the uppermost cell developing into the oogon- 

 ium whilst the lowest forms a short stalk. The middle cell cuts off 

 five peripheral cells which grow up in a spiral fashion and invest 

 the oogonium, each one finally cutting off two small coronal cells 

 at the apex. The oogonial cell cuts off three cells at its base and it is 

 maintained that these, together with the oogonium, represent four 

 quadrants, only one of which develops to maturity. When mature, 

 the investing threads part somewhat to form a neck, and the apex 

 of the oogonium gelatinizes in order to permit the antherozoids to 

 enter. After fertilization the zygote nucleus travels to the apex of 

 the oospore and a coloured cellulose membrane is excreted around 

 it, whilst the oogonium wall, together with inner walls of the in- 

 vesting threads, thicken and siUcify. Four nuclei are formed by 



