16 FRESH-WATER ALG^ OF THE UNITED STATES. 



Family OSCILLARIACE^. 



Trichomata simplicia baud vero multicellularia, sed distincte articulata, plerumque vaginata, mo- 

 tiouibus variis pnudita. 



Filaments simple, not strictly multicellular, but distinctly articulate, mostly vaginate, moving in 

 various ways. 



Genus OSCILLARIA, Bosc. 



Trichomata simplicia, plerumque distincte articulata, rigida, recte vel parum curvata, rarius cir- 

 cinata vel spiralitcr convoluta, plerumque tete colorata, motu triplici psedita, in muco matricali 

 nidulantia vel vaginula tubnlosa angustissima utroque fine aperta iuclusa; articuli fronte disciformes. 

 (R.) 



Filaments simple, mostly distinctly articulate, rigid, straight, or somewhat curved, very rarely 

 circinate or spirally convolute, capable of three motions, floating in a maternal jelly, and shut up 

 in a fine tubular sheath, open at both ends ; joints from the front disciform. 



The oscillaria are very peculiar plants, which flourish almost in every situation 

 in which fresh water is to be found. The purest springs are not always free from 

 their presence, although they occur most abundantly in stagnant pools and ditches, 

 where animal or vegetable matters are undergoing decay. AVhen viewed in mass, 

 floating upon some foul pool, few objects in the vegetable world are better calcu- 

 lated to excite disgust. A dark, slimy scum reeking with its putrescent surround- 

 ings, they seem to ofter nothing of pleasure or interest. But, when brought home 

 to the table of the microscopist and placed beneath his object-glass, they startle 

 the observer by the wonders of their life-history. Living rods, writhing, twisting, 

 bending, curling, creeping, gliding hither and thither ; incessant, apparently cause- 

 less, motion, occurring too in what to most minds is the very type of fixity and 

 passivity — a plant. No marvel, then, that they are so famous. 



The structure of an oscillatoria is about as simple as it can be. An outside 

 colorless cellulose sheath, which is probably in the uninjured filament closed at the 

 end, although, as seen by the microscope, violence and age have often torn it open. 

 Within is a long rod of variously colored endochrome, distinctly articulated by, at 

 great or less intervals, breaks in the color, which appear as dark lines under a low 

 power, but, under a higher objective, arc revealed as narrow linear portions of 

 protoplasm lighter and more transparent than the rest. Frequently at the joints 

 there is a marked tendency to separation between the successive articles, and a very 

 decided contraction of the endochrome on each side, so as to leave a little gutter, 

 or dividing trench. The endochrome is sometimes homogeneous, sometimes con- 

 tains numerous granules, which are, however, never amyloid in their nature. 



The color of the endochrome varies very greatly in the difl"erent species. Slate 

 color, blue, greenish, olivaceous, are among the most common hues. According 

 to Dr. Ferdinand Cohn (Botan. Zeitimg, 1867, p. 38; Sitzung, 13th Dec. 1866, 

 der Schlesischen Gesellschaft fiir vaterliindische Cultur), the coloring matter of the 

 oscillatoria consists of true chlorophyll, and a substance which he calls Phycocyan, 

 but which he states to be diff"erent from Phylwhyan of Kiitzing, the Phyr^iocJirom 

 of Nirgcli, and also from Phycwyun of the latter authority. The chlorophyll is, 



