COLOUR, DISTRIBUTION, ETC. 19 



There are certain physical influences which affect Sea- 

 weeds, and to some of these I will now refer as briefly 

 as possible. 



I' will first revert for a moment to the whole family of 

 Algas, to state that the only conditions indispensable to 

 their existence are the presence of air and moisture. 

 They will grow in the waters of mineral springs, no 

 matter how hot or how cold; in vats of poisonous 

 chemical solutions ; in dark caves ; and amid the Arctic 

 snows. Even the nebulous vapours high above the sur- 

 face of the earth are supposed to afford them a suffi- 

 ciently hospitable shelter. Notwithstanding, however, 

 this almost universal diffusion of certain of the lower 

 Orders, the more perfect members of the class are all 

 natives of the sea, and thence derive their name oiAlgce, 

 or Sea-weeds, the latter name being but a translation of 

 the former. With few and unimportant exceptions, 

 such as Zostera marina, — the grass which grows so abun- 

 dantly on many muddy shores between the tide-marks, 

 and which was proposed as a substitute for cotton during 

 the recent scarcity of that fibre, — the entire vegetation of 

 the ocean is composed of Sea-weeds. The hardy Fuci 

 make their appearance on the first rocks that escape the 

 rigorous grasp of perpetual ice in Arctic and Antarctic 

 latitudes, and thence with ever-increasing variety of 

 forms, and, as a rule, with greater and greater luxuriance 

 of growth, the Nereid multitude rolls on north or south 

 until it culminates in the perfection of its fairy radiance 

 and beauty in the hottest regions of the tropical seas. 

 Rocks are everywhere the chosen haunts of the majority 

 of Sea-weeds, which do not appear to have much predi- 

 lection for any particular kind ; nor indeed is this won-, 

 derful, for they seek them for shelter and for foothold, 



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