112 



CHLOROPHYCEAE 



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 peculiar group. 



Oogonia. Fig. 77. 



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

 row of three cells, the uppermost cell developing into the oogonium 



Fig. 77. Charales. A-F, Chara vulgaris, stages in formation of oogonium. 

 A, first division. B, C, division of periphery to form envelope cells. D, coronal 

 cells cut off. F, mature oogonium. G— I, Nitella flexilis, stages in formation of 

 oogonium. J, fertile branch of C. fragilis. a = oogonium, 6c = bract cell, hn = 

 branch nodal cell, ff= coronal cells, e = envelope cells, /= flask cell, z = internode, 

 w = nodal cell, f = turning cell, 0^ = oogonium stalk cell. (After Grove.) 



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 



