CYANOPHYCEsE 



445 



short oblong rods, which oscillate slowly and are not enclosed in a gela- 

 tinous sheath. In B. trilocularis (Cohn) each hormogone is composed 

 uniformly of three pseudocysts only. 



Many of the Oscillariaceae enter largely into the composition of the 

 blue-green scum seen on the surface of stagnant ditches, &c. Together 

 with others of the Nostochinese they are said 

 to have the power of decomposing vegetable 

 matter, and to this is largely due the foul 

 stench of stagnant water. In addition to 

 many species of Lyngbya a few belonging 

 to other genera grow in salt or brackish 

 water. Several species of Oscillaria are 

 found in thermal springs. 



The relationship of the genera of 

 Oscillariacese to one another, and even 

 to genera at present included in other 

 families, is still very obscure. Hansgirg 

 believes that many of the forms described 

 as species of Chroococcus result from the 

 breaking up of filaments of Lyngbya ; 

 while, on the other hand, most of Kiit- 

 zing's species of Leptothrix, and many 

 of Oscillaria, may be simply hormogones of species of Rivulariaceae, 

 Scytonemeae, and Stigonemese, propagating by frequent divisions, and 

 becoming invested in a more or less thick gelatinous sheath. Many 

 species of Lyngbya may be only the young stages of development of 

 those species of Calothrix and Scytonema to which they are found 

 attached. Oscillaria or Lyngbya antliaria (Hansg.) he now regards as in 

 reality an Aphanocapsa. The same author further states that in the 



FIG. 372. Symfiioca hydnoides Kt/. 

 (a, natural size ; b, x 200). (After 

 Hauck.) 



FIG. w^.Symploca violacea Hauck ( X 280). (After Hauck.) 



Lyngbyese and other of the higher families- of Cyanophyceae, nuclei, 

 pyrenoids, and chromatophores occur, but only when they are in a con- 

 dition of retrogression from the filiform stale, and are breaking up into 

 the unicellular condition. Under the name Chroomonas Nordstedtii 

 Hansgirg describes (Bot. Centralbl., xxiii., 1885, p. 229) a biciliated 



