Xll DESMIDS OF THE UNITED STATE-. 



do. nearly two.huudred feet across their mariue 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, but 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 forests, or form floating islands 

 miles in diameter, where multitudes of marine creatures find 

 permanent homes. 



Equally diversified is their rauge of habitat ; no geonomic 

 condition suffices to exclude the Algce : they greet the traveler 

 on the confines of vegetation, near the highest mountain tops, 

 amid snow and ice', and are brought up by marine explorers 

 from great depths below the surface of the sea. 



To overlook their color would be to neglect a very striking 

 characteristic. The predominant tint of the entire class, in- 

 cluding both marine and fresh water varieties, is green ; then 

 pink grading off into all the shades of purple, and finally olive, 

 from golden green and bright tawny to black : indeed there are 

 few if any colors, from the most gorgeous to the dullest, but are 

 to be found among the Algce. They are also interesting for the 

 many useful purposes to which they have been and are applied. 

 We are under no small obligation to them for aiding to keep the 

 atmosphere in a wholesome condition, since they absorb carbonic 

 acid largely and exhale immense cxiiantities of oxygen. The 

 extinction of certain kinds would prove an annoying loss to our 

 materia medica. They nourish a large variety of fish and molusca, 

 and in some localities, constitute a nutritious fodder for cattle 

 and pigs ; moreover, of some kinds there are made sauces, soups 

 and blanc mange which are highly appreciated by epicures, 

 ■while others as fertilizers, are largely used by sea-coast farmers. 



Of what further benefit they may be to mankind it would be 

 rash to predict, but it is within the bounds of probability, that 

 the microscopic study of the fresh-water varieties, if pursued 

 hereafter as ardently as during the past few years, will result in 



' In a recent publication by V. B. Wittrock, of the Scientitic Academy of 

 StoclvholDi, he describes the Snow and Ice flora of the Arctic Zone. The 

 Snow flora comprises about 40 species and varieties of fresh-water Alga:, and 

 the Ice flora about 10 species. They belong to 25 genera. Ten species and 

 varieties are new. 



