x ii DESMIDS OF THE IMTKI' STATES. 



microscopes, while others are a constant source of astonishment 

 because of their enormous size, stretching as some of them do, 

 nearly two hundred feet across their marine beds, and with stems 

 sufficiently thick wherefrom to manufacture handles for small tools 

 and cutlery. 



Those which consist of only a few cells, contrast very forcibly 

 with others which in appearance, bul in appearance only, present 

 the branches, stems, twigs and foliage of highly developed plants; 

 nor are they less opposite" in what may be termed their sociality, 

 from the fresh-water hermits scattered more or less sparsely in 

 secluded places, up to those immense aggregations in mid ocean 

 which resemble sub-aqueous forestB, or form floating islands miles 

 in diameter, where multitudes "f marine creatures find permanent 

 homes. 



Equally diversified is their range of habitat; no geonomic con- 

 dition suffices t" exclude tin' Alga : they greet the traveler on the 

 confines of vegetation, near the highest mountain tops, amid -now 

 and ice 1 , and are broughl up by marine explorers from great depths 

 below the surface of the sea. 



To overlook their color would l>e i" neglect a verj striking 

 characteristic. The predominant tint of the entire class including 

 both marine and fresh water varieties, is green : then pink grading 

 oil' into all the shades of purple, ;ind finally olive, from golden 

 green and brighl tawny to black: indeed there .ire tew if any 

 colors from the most gorgeous to the dullest, but are to be found 

 among the Algce. They are also interesting tor the many useful 

 purposes to which they have been and are applied. \\ e arc under 

 no -mall obligation to them for aiding to keep the atmosphere in a 

 wholesome condition, since they absorb carbonic acid largely and 

 exhale immense quantities of oxygen. The extinction of certain 

 kinds would prove an annoying loss to our materia medusa. I hey 

 nourish a large variety of fish and molusca, and in some localities, 

 constitute a nntricious fodder for cattle and pigs; moreover, of 

 some kinds there are made sauces, soujxs and blanc-mange which 

 are highly appreciated by epicures, while others as fertilizers, are 

 largely used by sea^-coast farmer--. 



1 In a recent publication by V. I'-. Wittrock, of the Scientific Academy ol Stock- 

 holm, he describes the Nmu and I'' flora of the Arctic Hone. The Snow flora 

 comprises abVul 10 species and varieties of fresh-water Algtr, and tin- \>< flora 

 about L0 species. They belong i" "J~> genera. Ten specie* and new. 



