The English flora - SeaweedAfrica

Oscillatoria.] ALG.E CONFERVOIDE.E. 377
filaments are rather thick, about a line in length, straight or variously
curved, of a greyish-green colour, and they radiate with great rapidity.
A portion of the stratum, not more than a line in diameter, placed on a
watch-glass, filled with water, overspread the whole area of the glass with
filaments in the course of a night." Carm. MSS. A fine species ; in
a dry state strongly resembling black satin. The striated stratum
affords an excellent " prima facie" character.
18. O. Corium, Ag. (leathery Oscillatoria) ; stratum thick
subcoriaceous opaque dull-brownish streaked with pale-green,
filaments yellowish slender, striae indistinct distant. Ag. Syst.
Alg. p. 64. Lyngb. Hydroph. Dan. p. 89. Grev. Fl, Edin.
p. 303.
On the rocky bottoms of alpine rivulets; common.—Stratum thick,
tough, dull-brownish,
some varieties, is the
occasionally streaked with pale-green, which, in
prevailing colour, slightly glossy when dry; filaments
slender. In some situations it radiates fasciculately from its
whole upper surface; in others, it is found almost denuded of radii and
forming a compact leathery stratum.
19. O. subfusca, Vauch. (brownish-green Oscillatoria); stratum
dull greyish-brown somewhat streaked with a green shade
soft void of tenacity, filaments very slender hyaline straight,
stria? inconspicuous. Lyngb. Hydroph. Dan. t. 26. Ag. Syst.
Alg. p. 69.
Rocks and stones, in sub-alpine rivulets.— Stratum extensive, " soft,
slimy, void of tenacity, wrinkled, of a dusky-grey colour," (Carm.)
when dry greyish-brown, streaked with green towards the edges ; filaments
very slender, striae invisible.—Differs from the last chiefly in being
more gelatinous and fragile.
20. O. violdcea, Johnston, (purple Oscillatoria); "mass
gelatinous dark purple, filaments very slender straight without
perceptible transverse stria? laid on a thin compact greenish
substratum." Johnst. Beriv. Flora, r. 2. p. 264.
Rapid streams j near Berwick-upon-Tweed, Dr. Johnston, who con-
siders this the " Co///., mucosa confragosa, rivulis innasceos" of Dillenius.
21.