4. Oscillatoria tenuis Ag.
Plate L X X I I . Fig. 1.
Char. Stratum rich dark green, very thin, gelatinous, with
short rays. Filaments pale green, straight. Striæ subdistant,
evident.
Orev. Edin., p. 303. ; Harv. in Hook. Brit. Flor. 374. ;
Harv. in Manual, p. 163. O. limosa Hook. Scot. ii.
p. 79. Conf. limosa Dillw. t. 20. O. viridis Johnst.
Berw. Flor. p. 264.
Hab. Common in ditches.
“ In muddy ditches, at first resting at the bottom, but gradually
rising in bullated strata to the surface, common; stratum
extensive, glossy when dry, in Avhich state it fully preserves
its colour. Filaments, of half the diameter of those of O. limosa,
pale green; striæ distant and indistinct. I t adheres
strongly to paper.” — Harv. The stratum of this species
exactly resembles that of O. limosa, and the filaments, like it
also, contract somewhat in drying ; they are, however, two
or three times smaller ; the striæ more distant, and not so
strongly marked.
5. Oscillatoria cyanea Ag.
Char. “ Glaucous blue. Filaments simple, entangled, cylindrical,
even, with a deciduous coat. Joints obsolete, about
as long as broad.” — Sm.
Harv. Hook. Br. Fl. p. 374. Conferva cyanea, E. B.
t. 2578.; Harv. Manual, p. 163.
Hab. Damp walls on the inside of several Suffolk churches ;
at Icklingham and Hengrave; also in Lincolnshire: Sir
Thomas Gage, Bart.
“ On the wall it is conspicuous for its light sky-blue colour,
like some sort of mucor. Under a high magnifier, and
when moistened, it is found to consist of minute, even, simple,
entangled threads, one five hundredth part of an inch in diameter,
coated with a frequently Interrupted covering of a
dull glaucous green hue, under which the thread itself appears
of a lighter glaucous bluish colour, very even in thickness
and surface, consisting of scarcely distinguishable joints,
about as broad as they are long.”— Sm.
6. O s c il l a t o r ia æ r u g e sc e n s Drum.
Plate L X X I I . Fig. 2.
Char. Stratum o/' a fin e deep green, highly gelatinous ; when
dried, æruginous blue, and glossy. Filaments slender,
opaque green. Striæ evident.
Drummond, in Ann. Nat. Hist. vol. i. p. 1. ; Manual of
Brit. Alg. p. 163.
Hab. Lakes of Glaslough, co. Monaghan, Ire land: Dr.
Drummond. Farnham: Mr. Jenner. Bottom of pools
near Stocket, Aberdeen : Dr. Dickie.
“ Filaments exceedingly slender, opaque green ; conglomerated
in large toughish glutinous masses, in sheltered, calm
situations, and rarely floating on the surface ; in more open
exposures, broken into innumerable fragments, and suspended
like cloudy flocculi in the water. Striæ numerous, at distances
of about half a diameter from each other. Oscillatory
movement often lively. Colour when dried, a beautiful
æruginous blue ; adheres strongly to paper, exhibiting a glossy
surface. Filaments expanded by moisture so as to seem recent,
and sometimes resuming the oscillatory motion.” —
Dr. Drummond.
This species may at once be distinguished when dried from
all others by the peculiarly dense and waxen appearance of
the stratum, which also exhibits numerous fissures. The filaments
are smaller than those of O. tenuis, and the striæ closer.
They are likewise brittle, and when dried break up into very
short pieces, which are not of uniform diameter.