STRUCTURE AND DEVELOPMENT. 



45 



the antheridia and oogonia are produced together on 

 the inner side of the branchlets from one outgrowth 

 arising from the central anterior peripheral cell of 

 the branchlet-node taking the place of a bract-celL 

 In Lamprothamnium the oogonium is produced below 

 or occasionally by the side of the antheridium (Fig. 

 16 iv A and B), in Chara the antheridium is produced 

 below the oogonium (Fig. 17). Both oogonia and anthe- 



FIG. 17. Position of reproductive organs in Chara fragilis (after 

 Strasburger) ( x c. 45). Vertical section of branchlet-node and 

 reproductive organs, n, central cell of node ; i, internodal cells; bn, 

 basal nodal cell ; f, flask-cell of antheridium ; p t peripheral cells ; 

 c, cortical cells ; os, stalk-cell of oogonium ; be, bract-cell. 



ridia in these genera are almost always practically 

 sessile, but instances occur occasionally in which the 

 stalk-cell of one or other is elongated. 



The origin of the reproductive organs will be best 

 seen in Fig. 17. The oogonium is borne on a stalk- 

 cell os, and this, as well as the flask-cell of the 

 antheridium, arise from the cell bn called the basal- 

 node-cell. The order of development and the arrange- 



