SECT, xxvii.] DISTRIBUTION OF MARINE PLANTS. 305 



as grasses and palms which have only one seed-lobe, are to 

 the dicotyledonous tribe, which have two seed-lobes like 

 most of the European species, in the proportion of one to 

 four ; in the temperate zones they are as one to six ; and in 

 the Arctic regions, where mosses and lichens, which form 

 the lowest order of the vegetable creation, abound, the pro- 

 portion is as one to two. The annual monocotyledonous and 

 dicotyledonous plants in the temperate zones amount to one- 

 sixth of the whole, omitting the Cryptogamia (K 214) ; in 

 the torrid zone they scarcely form one-twentieth, and in 

 Lapland one-thirtieth part. In approaching the equator, the 

 ligneous exceed the number of herbaceous plants ; in America 

 there are a hundred and twenty different species of forest 

 trees, whereas in the same latitudes in Europe only thirty- 

 four are to be found. 



Similar laws appear to regulate the distribution of marine 

 plants. M. Lamouroux has discovered that the groups of 

 alge,or marine plants, affect particular temperatures or zones 

 of latitude, though some few genera prevail throughout the 

 ocean. The polar Atlantic basin, to the 40th degree of north 

 latitude, presents a well-defined vegetation. The West 

 Indian seas, including the Gulf of Mexico, the eastern coast 

 of South America, the Indian Ocean and its gulfs, the shores 

 of New Holland, and the neighbouring islands, have each 

 their distinct species. The Mediterranean possesses a vege- 

 tation peculiar to itself, extending to the Black Sea ; and 

 the species of marine plants on the coast of Syria and in the 

 port of Alexandria differ almost entirely from those of Suez 

 and the Red Sea, notwithstanding the proximity of their 

 geographical situation. It is observed that shallow seas have 

 a different set of plants from such as are deeper and colder ; 

 and, like terrestrial vegetation, the algae are most numerous 

 towards the equator, where the quantity must be prodigious, 

 if we may judge from the gulf-weed, which certainly has 

 its origin in the tropical seas, and is drifted, though not by 

 the gulf-stream, to higher latitudes, where it accumulates in 



