THALLOPHYTA. 



665 



number of irregular fleshy lobes, which are produced into branching, whip-like 

 filaments. Its tissues possess a curious honey-combed structure. It is stated that 

 in Chili, &c., D. utilis is used as an article of food. Sargassum is distinguished by 

 its high differentiation. It has cylindrical stalks bearing leaf -like appendages, and 

 little stalked spherical air-bladders, and receptacles for the sexual organs. Some 

 150 species of this very varied genus are known, scattered over the warmer zones 

 of the world. Particular interest attaches to the Gulf -weed (Sargassum bacciferum, 

 fig. 378) which forms the chief component of the floating masses of Sargassum in 

 certain regions of the Atlantic. 

 The Sargasso Sea has received its 

 name from the enormous amounts 

 of this floating weed which are met 

 with there. It occupies an area in 

 the Atlantic perhaps equal to that 

 of the continent of Europe. There 

 are two main accumulations, the 

 larger south-west of the Azores, the 

 smaller situated between the Ber- 

 mudas and Bahamas, whilst connect- 

 ing them is a narrow belt. The exact 

 nature of these accumulations is not 

 ascertained. According to one view 

 the Gulf -weed actually lives a pelagic 

 life, growing and multiplying in this 

 huge eddy in mid-ocean, and is 

 thoroughly adapted to its special 

 environment; whilst, on the con- 

 tending hypothesis, the vegetation of 

 the Sargasso Sea is purely ephem- 

 eral, does not reproduce, and is con- 

 stantly renewed by ocean currents, which bring with them countless fragments 

 forcibly torn by tempests from the shores of Florida and the Bahamas. It is further 

 alleged that the floating Gulf -weed is met with only in a condition more or less 

 unhealthy (moribund) and in various states of decomposition. 



The weak point in the latter hypothesis is the lack of convincing evidence to 

 show that 8. haccifermti grows attached in the region of the West Indies, &c., in 

 quantity sufficient to supply the Sargasso Sea. Of another species, 8. vulgare, 

 there is plenty, but this is not the prominent constituent of the Sargasso Sea— 

 indeed a trained algologist, in passing recently through this sea, examined samples 

 amounting to more than a ton, but it was only 8. bacciferum he found. Here, 

 evidently, is still matter for the leisured naturalist. 



Over 300 species of Fucacese (including 150 Sargassums) have been distinguished. 



fig. 378.— A branch of the Gulf-weed, Sargassum lace\ferwm, 

 with leaves and air-sacs. 



