GULFWEEDS (SARGASSUM) 



323 



and are ])orno in sex organs, whicli are also (juitc unlike. Tlie s(>x 

 organs are borne in hollow eonceptacles, wiiicli occur in large 

 numbers in the swollen tips of the branches. Each conceptacle 

 opens to the exterior by a pore-like opening. In this species the 

 male and female sex organs do not occur together in the same 

 eonceptacles as they do in some species. The oogonium is a 

 large, globular, stalked cell and in this species contains eight eggs, 

 but the number ranges from one to eight in other species of 

 Fucus. The antheridia are borne 

 on the lateral branches of much- 

 branched filaments, which pro- 

 ject from the wall of the concep- 

 tacle. They are oval cells which 

 produce numerous sperms. A 

 curious feature of Fucus is that 

 the eggs as well as the sperms are 

 discharged from the conceptacle 

 before fertilization. The eggs 

 while passively floating about 

 are surrounded by swarms of 

 spcTms, which sometimes, by their 

 vigorous movements, give the 

 eggs a rotary motion. In fertil- 

 ization one sperm, after pene- 

 trating the cytoplasm of the egg, 

 fuses with the egg nucleus and 

 thus an oospore is formed which 

 develops a new plant. 



Gulfweeds (Sargassum). — 

 The Gulfweeds, well known in 

 connection with the Sargasso Sea, are sometimes a meter in 

 length and are more differentiated than the Rockweeds (Fig. 

 279). In form the stalks and leaf-like branches resemble very 

 much the stems and leaves of the higher plants, although they 

 are very different in structure. The stems are at first anchored 

 by root-like holdfasts and bear many stalked air bladders, which 

 buoy up the plant when attached and float it when torn free. 

 Other short, thick, axillary branches contain the eonceptacles. 

 So far as known their reproduction is similar to that of the Rock- 

 weeds. 



Fig. 279. — A portion of a plant 

 of Sargassum vulcjcire, showing the 

 floats and the stem- and leaf-like 

 structures. X h- 



