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 

 the tips of the short branches. Since the branches bear 









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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. (After 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 



