2. N ostoc commune Vauch.
Plate L X X IV . Pig. 2.
Chai'. Frond terrestrial, expanded, membranaceous, plaited,
waved, or curled; olive green, shining, and irregular in
form. Filaments thick, heautifidly moniliform. Reproductive
cells larye, either attached to the filaments, or hjing
scattered throughout the frond.
Nostoc commune Vauch., Hist, des Conf. p. 223. pi. xvi.
f. 1. Ti'cmella Nostoc, Fng. Bot. t. 461. Tremella terrestris
Dill., Muse. p. 52. t. 10. f. 14.; Harvey in
Manual, p. 183.; Meneghini, Monographia Nostochine-
arum Italicarum.
Ilab. “ Gravelly soils, garden walks, rocks, pastures, &c.;
very common in autumn and winter.”
The filaments arc large, exactly moniliform, fiexuous, and
copious, with here and there an enlarged reproductive cell of
an exactly spherical form. These enlarged cells occur either
in the course of the filaments, are terminal, or lie detached in
the mucous matrix of the frond. Some writers have laid
great stress, in their descriptions, upon the fact of these
globules being so frequently terminal. This position of them
has nothing to do with the developement of the species, but
arises from the thread of which they formed a link having
separated from one side of them — a step preparatory to their
being altogether cast off" by the filaments.
“ In prima tantum hujusce specie! astate deprehendenda
est interior substantia aquosa-gelatinosa, qua cito elapsa
frons excavata potius quam vesicEeformIs efficitur, stratum
enim periphericum, ratione habita cavitate interior!, multo
crassius est in cseteris omnibus speciebus.” — Menegh.
The only species with which there is any danger of confounding
Nostoc commune are, N. cccruleum and N.foliaceum.
The filaments of N. commune correspond in size and appearance
very closely with those of N. cccruleum, but the external
characters are altogether distinct; the contrary is the case
with N. foliaceum, the external characters resembling those
of N. commune, but the filaments are different, being much
smaller in size, although, like those of N. commune, distinctly
moniliform.
3. N ostoc foliaceum Ag.
Plate L X X V I . Fig. 2.
Char. Frond membranaceous, erect, plaited, olive green.
Filaments slender, copious, moniliform. Fnlarged globuli
numerous.
Nostoc foliaceum Ag., Syst. p. 19.; Harv. in Hook. Br.
Flora, ii. p. 399. ; Harv. in Manual, p. 184. ; Meneghini,
Monographia Nostocliinearum Italicarum, vol. v. p. 18.
serie ii. delle Memorie della E. Academic delle Scienze
di Turino.
Hah. On clayey ground kept constantly damp by the
oozing of water, Appin : Capt. Carmichael. Ireland ;
Mr. Moore.
“ This species is easily distinguished both by its appearance
and station from Nostoc commune, to which it seems similar,
as respects certain external characters. I t never swells up
into the form of a vesicle ; the structure, altogether uniform,
extends as a membrane, and rises up hy moisture into plicated
lobes : it grows on stones, and is evolved, the winter scarcely
being ended, when Nostoc commune has not yet appeared.” -—
Menegh. The difference in the size of the filaments of Nostoc
commune and N. foliaceum is perhaps the only character
whereby the two species can at all times be discriminated,
the threads being much smaller in the latter species.
4. N ostoc sphìericum Vauch.
P late L X X V I . Fig. 5.
Char. Frond small, globose, densely aggregated, solid, smooth,
olive green, watery within. Filaments small, moniliform.
Nostoc sphcericum Vauch., Conf. p. 223. pi, xv. f. 2.