Chap. II] 



MARINE VEGETATION 



791 



on the surface of the sea often far away from the coast. The phenomenon 

 is specially striking in the tropical Atlantic and has given rise to the 

 fabulous account of a ' Sargasso Sea,' 

 where the Alga, possibly always 

 Sargassum bacciferum, is said to form 

 floating meadows (Fig. 480). Only few 

 species of Algae, at least among those 

 of wider distribution, are confined within 

 the tropics ; most of them also occur 

 outside the tropics in warmer parts of 

 the ocean. It will therefore be necessary 

 to extend the tropical zone of marine 

 vegetation beyond the tropics both north- 

 wards and southwards. Yet even in the 

 Mediterranean Sea phenomena of plant- 

 life occur, which are connected with the 

 change of seasons in the temperate climate 

 and which are inconceivable in the tropics. 

 The benthos-vegetation of the tropical 

 sea is at present very insufficiently known. 

 No scientific traveller appears to have 

 made it the subject of detailed investiga- 

 tion. During my travels in the tropics 

 I did not pay any special attention to the 

 matter. Compared with the coasts of 

 more northern seas, those of the Riviera 

 for instance, the emerging belt appeared 

 to me singularly poor in Algae in the 

 Lesser Antilles, on the rocky coasts near 

 Singapore, and on the coast of Java. 

 Yet an exception is provided in both 

 the New and Old Worlds by the man- 

 groves, where the roots and stem-bases 

 within reach of the tides exhibit a thick 

 coating of dirty violet Florideae (in South 

 Brazil, Catenella impudica, Kiitz., and 

 Bostrychia radicans, Mont., f. brasiliana) 1 . 

 A very cursory examination of the sub- 

 merged belt on the coral reefs of the 

 Java Sea gave only slight results. A 

 species of Halimeda, probably H. Opuntia, which occurred everywhere, and 

 had frequently been thrown up on the reef, formed the sole exception. 

 1 Determined by Prof. M. Mobius, and communicated by Prof. H. Schenck. 



Fig. 4S0. Sargassum bacciferum. Natural 

 size. After Kiitzing. From Strasburger's 

 Text-book of Botany. 



