Fig. 376. OSCILLATOKIA SUBULIFORMIS. 



Colour. The layer looking blackish imder water; when taken out a deep beautiful 



blue-green ; filaments bright green. 

 Substance. The layer soft; gelatinous. 



Character of Frond. A thinnish layer of very slender threads {filaments), awl- 

 shaped, with pointed tips; at first growing on mud, afterwards floating. 

 Filaments apt to break into needle-like fragments; unbranched; tubular; 

 containing bright green colour-cells, which show through ; their division-lines 

 inconspicuous 3 set at intervals of from half to three-fourths the width of the 

 filament. 



Ileasurement. Indefinite. 



Fructification. As before. 



Habitat. Shirehampton, Bristol, In a brackish ditch. Found with the preceding, 

 O. nigro-viridis. 



The oscillations of O. suhuliformis are very vivid. 



Fig. 377. OSCILLATOKIA INSIGNIS. 



Colour. The layer dark brown, almost black; filaments brown. 

 Substance. Soft; gelatinous. 



Character of Frond. A thin layer of large brittle threads {filaments'), slightly 

 curved, with blunt tips fringed with short, cobweb-like fibres. Filaments 

 apt to break into needle-like fragments; unbranched; tubular; containing 

 brown colour-cells, which show through; their division-lines conspicuous and 

 very close. 



Measurement. The layer indefinite; filaments larger than those of any other marine 



Oscillaioria. 

 Fructification. As before. 



Habitat. Shirehampton, near Bristol. In a brackish ditch. Found with the two 

 preceding. 



The fringed tips occur in other Oscillatorias, but are more easily observed 

 in this one, from the much greater thickness of the filaments. 



Fig. 378. MONORMIA INTEICATA. 



Colour. At first olive-yellow; gradually greenish; when dry, deep verdigris-green. 

 Substance. Very gelatinous and soft. 



Character of Frond. A small, roundish, floating mass; formed of single threads 

 {filaments), densely curled and twisted; immersed in loose, gelatinous, tube- 

 like cylinders; several times branched. Filaments formed of globose cells, 

 filled with colouring matter {endochrome) ; strung together; a larger cell, of 

 difl'erent character, interrupting the uniformity here and there (a microscopic 

 object). 



Measurement. The little mass J of an inch across. 



Fructification. Minute seeds {zoospores) formed of the colouring matter in the 

 usual cells of the filaments, and in due time bursting through them. 



Habitat. Gravesend. In the ditches of the marsh to the south of the Frindsbury 

 canal. Very abundant. 



Sometimes found with, and even inside, Enteromorplia intestinalis ; and in 

 fresh water. 



84 



