74 MARINE ALG^E 



is a tropical and subtropical genus, and has one hundred and 

 fifty species. Two of these, 8. vulgare and 8. Montagnei, are found 

 as far north as Cape Cod. See Introduction, page 34. 



S. vulgare. Stems cylindrical ; branches alternate ; leaves long, 

 narrow, toothed, with short stalk and midrib ; minute dark spots on its 

 surface ; air-vessels small balls resembling berries set on stalks and 

 usually tipped with a long point ; receptacles small, twig-like forms 

 in the axils of the leaves ; color olive-brown ; plant one foot to three 

 or more feet long. Common in Long Island Sound. (Plate XVI.) 



S. Montagnei. This species resembles S. vulgare, but is more slender 

 in all its parts, and the receptacles are more elongated. Prom south of 

 Cape Cod. 



S. baccifenim. Particular interest attaches to this species from the 

 fact that it is the one which forms the floating vegetation of the Sargasso 

 Sea. It grows attached on the Florida Keys and in the West Indies. 

 Specimens are sometimes carried by the currents northward, and are 

 found washed ashore. It differs from S. vulgare in the leaves, which 

 are thicker, more attenuated, and sharply toothed, and in having a 

 greater number of air-vessels. A branch of this species brought from 

 the Sargasso Sea had air-vessels so numerous and closely set that it 

 resembled a bunch of small grapes. 



