Dr Greville's Algos Brttannicce: > 363 



Seas of Okhotsk and Bhering, and the West Indian Sea, along wijh the 

 Gulf of Mexico, denominated by him The Columbian Mediterranean. 



" Every great zone presents a peculiar system of existence ; and it is said, 

 that after a space of twenty-four degrees of latitude a nearly total change 

 is observed in the species of organized beings, and that this change is;piainly 

 owing to the influence of temperature. Lamouroux remarks, that if this 

 holds good, as we know it to do, to a wonderful extent in phaenogamous 

 plants, it should also exert some corresponding force upon marine vegeta- 

 tion. It is unquestionable that the Algce are found on our own coast in the 

 greatest abundance during the summer months, and in unusual luxuriance 

 in hot seasons. It is probable also, observes the same author, that these 

 plants may be acted on by the temperature of the water at greater or less 

 depths ; and that the species which grow at the bottom of the ocean may 

 have some resemblance to those of the Polar circle. On the shores of the 

 British Islands it is easy to perceive that some species, Gelidium comeum, 

 Phyllophora ruhens, and Sphcerococcus coronopifolius, for example, become 

 more plentiful and more luxuriant as we travel from north to south ; and, 

 on the other hand, that Piilota plumosa, Rhodomela lycopoidiodes, Rhod- 

 menia sobolifera, and several others occur more frequently, and in a finer 

 state, as we approach the north. Odonthalia dentata and Rhodomenia cris- 

 tata are confined to the northern parts of Great Britain, while the Cysto- 

 seirce, Fucus tuberculaius, Haliseris polypodioides, Rhodomenia jubata, R. 

 Teediif Microcladia glandulosa, Rhodomela pinastroides, Laurencia tenuis^ 

 sima, Iridea reniformis, and many others, are confined to the southern 

 parts. Others again, such as the Fuci in general, the Laminariew, many 

 Delesserice, some JViiophyUwj Laureniice, Gastridia and Chondri^ possess 

 too extended a range to be influenced by any change of temperature be- 

 tween the northern boundary of Scotland and the south-western point of 

 England. The researches and calculations'of Lamouroux have demonstrat- 

 ed satisfactorily, that the great groups of Algoe do affect particular tempe- 

 ratures or zones of latitude, though some genera may be termed cosmopo- 

 lite. Setting aside the great division of articulated Alga, of which we 

 know but little, the SiphonecB, or at least the genus Codium, and the Ul- 

 vaceee, are scattered over every part of the world. Codium tomeniosum is 

 found in the Atlantic, from the shores of England and Scotland to the 

 Cape of Good Hope ; in the Pacific from Nootka Sound to the southern 

 coast of New Holland. It abounds in the Mediterranean, on the shores of 

 France, Spain, and Africa, and is common in the Adriatic. More recently 

 it has been also brought from the coasts of Chili and Peru. This plant, 

 however, is not a social one — to make use of a term that Humboldt has ap- 

 plied to some pha?nogaraous plants. It grows even in the same locality, in 

 a solitary and scattered manner. The Ulvaceoe, on the contrary, are strictly 

 social, and preserve this character in every part of the world. They ap- 

 pear, however, to attain the greatest perfection in the polar and temperate 

 zones, although I have very fine Porphyra from the Cape of Good Hope. 

 That they are capable of sustaining very extreme cold, is proved by the 

 fact, that fine specimens of Enteromorpha compressa were picked up in 

 high latitudes of the Arctic Ocean, by some of the gentlemen who accom- 



