Fig. 376. OSCILLATORIA SUBULIFORMIS. 
Colour. The layer looking blackish under water ; when taken out a beautiful deep blue-green ; 
filaments bright green. 
Substance. The layer soft ; gelatinous. 
Character of Frond. A thinish 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 ; set at intervals of 
from half to three-fourths the width of the filament. 
Measurement. Indefinite. 
Fructification. As before. 
Habitat. Shirehampton, Bristol. In a brackish ditch. Found with the preceding, 0 . nigro- 
viridis. 
The oscillations of O. subuliformis are very vivid. 
Fig. 377. OSCILLATORIA 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 Oscillatoria. 
Fructification. As before. 
Habitat. Shirehampton, near Bristol. In a brackish ditch. Found with the two preceding. 
The fringed tips occur in other Oscillatorias, hut are more easily observed in this one, from 
the much greater thickness of the filaments. 
Fig. 378. MONORMIA INTRICATA. 
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 different character, interrupt- 
ing the uniformity here and there (a microscopic object). 
Measurement. The little mass \ 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, Enteromorpha intestinalis ; and in fresh water. 
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