Oct. 31, 1878] 



NATURE 



709 



Atlantic. Almost every one who meets with the plant on his first 

 trip across the ocean brings home a small bottle filled with the 

 weed, which is shown to admiring friends, and then put away 

 and forgotten. But the plant is much too interesting to be thus 

 thrown aside without examination. Let the bottle be carefully 

 broken so that the gulf -weed may be removed without injury ; 

 then place it in salt water — in sea-water if it can be got — in a 

 large vessel of clear glass, where it will have room to expand, 

 and then will be seen its beauty and grace of form, no small 

 addition to which are the pretty and minute species of Cam- 

 panularia, Plumularia, and Sertiilaria which twine around its 

 branches, while other parts of the plant are covered by Polyzoa 

 with a delicate lace-work as hard as stone. 



But it is not only on account of its beauty that gulf -weed is 

 deserving of attention ; there is a history attached to it which 

 renders it one of the most interesting vegetable productions of 

 the sea. I propose, therefore, to give a summary of all that is 

 yet known respecting the habits and history of this plant. 



Whether the Sargasso Sea was known to the ancients is 

 doubtful. Two descriptions, by ancient writers, of a kind of 

 "Mar de Sargasso," near the coast of Africa, have been trans- 

 mitted to us. 



Humboldt ("Aspects of Nature," pp. 46, 47, Bohn's edition) 

 has shown that both these descriptions refer to localities too near 

 tlie coast of Africa to be applicable to the Sargasso Sea. The first 

 description is from a work which Humboldt says for a long time 

 bore incorrectly the name of Aristotle ; it is as follows : — " Phoe- 

 nician mariners came in a four days' voyage from Gades to a place 

 where the sea was found covered with rushes and sea-weed. The 

 sea-weed is uncovered at ebb, and overflowed at flood tide," There 

 are no rushes mixed with the sea-weed in the Sargasso Sea, neither 

 is the weed covered or uncovered by the water according to the 

 state of the tide. The second description, from the Periplus, 

 which has been ascribed to Scylax, of Caryanda, is thus quoted 

 by Humboldt : " The sea beyond Cerne ^ ceases to be navigable 

 in consequence of its great shallowness, its muddiness, and its 

 sea-grass. The sea-grass lies a span thick, and it is pointed at 

 its upper extremity, so that it pricks." Now the Sargasso bank 

 is in deep water, which is not muddy, and no sea-grass (which 

 inhabits shallow water) ever grows on it. The Sargasso bank is 

 much more than a span in thickness, and the upper extremity of 

 the plant is not sharp enough to prick. 



Columbus and his followers called the floating sea-weed 

 "sargazo," a term which botanists have modified into Sar- 

 GASSUM, as the generic name, adding, as the specific name, 

 bacciferum, alluding to the great number of berry-like air- 

 vesicles which a.-sist to buoy up the plant when in the water. 

 This alga is also sometimes called ^' Fucus nutans," on account 

 of its being found floating on the sea, and not attached to the 

 shore or to rocks, while to sailors it is known by the name of 

 "gulf- weed," and that part of the sea where it is met with in 

 greatest abundance is called the Sargasso Sea. 



The Sargasso Sea is situated in the North Atlantic, between 

 22" and 36° N. latitude, in the comparatively quiet space which 

 is bounded on the south by the great Equatorial current, on the 

 west and north by the Gulf Stream, and on the east by the 

 Guinea current, which flows southwards. Humboldt "^ states that 

 there are two principal banks, the lari^er of which lies a little to 

 the west of Fayal, one of the Azores ; the smaller near to the 

 Bahamas. The situation, however, of the weed-banks varies in 

 different seasons, according to the prevalent winds. Maury states ^ 

 that " an area equal in extent to the Mississippi Valley, is so 

 thickly matted over with gulf -weed, that the speed of vessels 

 passing throut^h it is often much retarded. When the com- 

 panions of Columbus saw it, they thought it marked the limits of 

 navigation, and became alarmed. To the eye, at a little distance, 

 it seems substantial enough to walk upon. Patches of the weed 

 are generally to be seen floating along the outer edge of the 

 Gulf Stream. The sea-weed always ' tails ' to a steady or 

 constant wind, so that it serves the mariner as a sort of marine 

 anemometer, telling him whether the wind, as he finds it, has 

 been blowing for some time, or whether it has just shifted, and 

 which way. Columbus first found this weedy sea on his voyage 

 of discovery ; there it has remained to this day, moving up and 

 down, and changing its position, like the calms of Cancer, 

 according to the seasons, the storms, and the winds. Exact 



' " The Phoenician station for merchant vessels (Gaulea) ; or, according 

 to GosseUn, the small estuary of Fedallah, on the north-west [coast of Mau- 

 ritiania." Humb. Idt, /^. 



* See " Views of Nature," Bohn's translation, p. 48. 



3 " Physical Geography of the Sea," p. 28, tenth edition. 



observation as to its limits and their range, extending back for 

 fifty years, assure us that its mean position has not been altered 

 since that time." Dr. Harvey says ^ that he had made the voyage 

 across the Atlantic four times, and only once found gulf -weed in 

 any quantity. It then occurred in ridges of great length from 

 ten to twenty yards in breadth. These ridges are separated by 

 water, which flows between them like rivers or lakes, 2 



One fact respecting the gulf-weed, hitherto unnoticed by 

 botanists, has not escaped the keen eye of the sailor, namely, 

 that the plants rise a few inches aboz'e the water, the upper 

 branches not being immersed ; hence it is readily observed from 

 a distance. It is this power of supporting the upper branches 

 out of the water in an erect position — a very unusual power in 

 sea- weeds — that enables the gulf -weed to " tail" to the wind, as 

 before mentioned. 



Another peculiarity attending the floating weed is that no 

 other marine plant has ever been found growing on it or with it ; 

 small zoophytes and polyzoa are, however, often attached to it. 

 Although its vegetation is limited to one species, the Sargasso 

 Sea is a great resort of animal life, and it lies within the 

 northern limits of the wanderings of the Sperm whale. The 

 Right whale sometimes crosses its northern boundary, where the 

 water is cooler. 



A third peculiarity affecting the floating gulf-weed is that it 

 has neither root nor fruit ; never in the Atlantic, or in other 

 localities where it is met with, has it ever been found in fruit. ** 

 On this point I shall have more to say hereafter. 



The genus Sargassimi is the most highly organised of the 

 Melanospermeae, or olive-coloured sea-weeds. It possesses root, 

 stem, branches, leaves, air-vesicles, and distinct organs of frac- 

 tification. The species are very numerous. Agardh, in his 

 " Species, Genera et Ordines Algarum," part i, published in 

 1848, describes 126 species, which number has since been 

 greatly increased. These species are classified into three 

 sections and twelve tribes. Gulf -weed belongs to the highest 

 section, namely, Eu-sargassum, or Sargassum proper, and to 

 the twelfth tribe Cymosze. 



The genus Sargassum inhabits the tropical and sub-tropical 

 seas of both hemispheres, extending on each side of the equator 

 to about the 45° parallel of latitude, gradually increasing in 

 number of species towards the line. With the exception of 

 .S". bacciferum (gulf- weed) and S, vulgare, which is also sometimes 

 called " Fucus nutans,^' * the species are very local. Thus some 

 grow on the coasts of Australia only, and the species of North 

 Australia differ from those of the south. A remarkable group 

 of Sargasso inhabits the coasts of Japan, where the plants grow in 

 the warm waters of "the Black Current," the Pacific analogue of 

 the Gulf-Stream of the Atlantic ; other species are found in the 

 China Seas, many in the Indian Ocean, and these are generally 

 distinct from those of the Red Sea. The section Cymosce, to 

 which Gulf-weed belongs, inhabit chiefly the Atlantic and 

 Indian Oceans and the Australian coasts. 



With these extremely local habits, and permanently distinct 

 species, it seems difficult to reconcile the errant habits and the 

 fixed forms of S. vulqare, and the plant which has given its 

 name to the Sargasso Sea ; both species are found in most of 

 the warmer seas in both hemispheres.^ Slight deviations some- 

 times occur in these plants, but they are clearly traceable to 

 local causes. Thus, in the Sargasso Sea, the plants have often 

 shorter leaves, the branches are contracted, and the bristles 

 of the air-vessels broken off"; whereas, specimens firom Sydney, 

 New South Wales, have longer leaves, the air-vessels have very 

 long bristles, which frequently form narrow leaves, and the 

 habit of the plants is more lax and straggling. 



S. zulgare produces fruit in all the localities where it is 

 found ; but, with regard to S. bacciferum, it has already been 



' " Manual of British' Algae. " Introduction, p. xxi., xxil., second edition. 



2 Besides the Sargasso-bank, in the Atlantic, Maury mentions several 

 other accumulations of sea-weed kn^wn to mariners as " Sargassos." The 

 immense banks of weeds in the South Pacific, through which ships pass in 

 going to the Australian colonies, consist principally of a pelagic form of 

 Macrocystis ; of the composition of the other weed-banks little is known. 



3 "Om de under Korvetten 7<?j<r//4/««.. expedition, sistlidensommar(i869) 

 insamlade Algeme." Af J. G. Agardh, Ofversigt af Kongl. Vetenskaps- 

 Akadentiens Forhandlingar, 1870, No. 4, Stockholm. 



* It is much to be regretted that this term " Fucus naiaru" should not 

 have been limited by authors to S. bacciforum. 



5 S. bacciferum is found in the Atlantic, between 22° and 58", being 

 sometimes carried on the Gulf Stream as far as the Orkney Islands. It is 

 also found on the coasts of Spain and Portugal, and in the Mediterranean 

 Sea, its presence in these localities also being due to the Gulf Stream. It is 

 likewise met with in the Indian Ocesui, the Pacific, on th« coasts of 

 Australia, and New Zealand. 



