232 



STRUCTURE AND LIFE HISTORIES 



212. Sexual Reproduction. The reproductive organs 

 of Ascophyllum (Fig. 174) are borne in chambers 

 (conceptacles) beneath the surface of the enlargements at 

 xhe tips of the short branches. Since the branches bear 



FIG. 174. Ascophyllum nodosum. A, Cross-section through a female 

 receptacle* B, spermagonia; C, ripe oogonium; D, eggs, freed from the 

 oogonium, but still enclosed by the separated inner layer of the oogonial 

 wall. (Redrawn from Thuret and Bornet.) 



the gametes they are sometimes referred to as gameto- 

 phores. These chambers open to the exterior by short, 

 narrow canals, the openings of which may be easily seen 

 on the surface of the swollen tips. The inner surface of 



