V ;
h u
“ Immediately distinguishable from its congeners on account of its
possessing a definite gelatinous sheath to each of its filaments, -which
are of smaller diameter than those of any other speoies of DoUchosper-
mum. The ordinary cells are subspherical, somewhat compressed, and
of less diameter than the heterooysts, which are barrel-shaped, and
with very distinot puncta. The numerous spores, which are about twice
the diameter of the ordinary cells, are elongated and cylindrical, very
variable in length and in the number which occur together, and their
ends are slightly truncate.”—Ralfs.
Plate X C I I I . fig . 7. Portions of trichomes with heterooysts and
spores X 400 ; fig. a from Scandinavian specimens ; fig. 6 from British
specimens.
Anabaena. o sc illa x io id e s. Bory. Diet. Hist. Nat.
Forming a bluish green stratum.
Trichomes elongated flexuous, joints subquadrate, distinct ;
heterooysts barrel-shaped or elliptic. Spores oval, catenate,
somewhat larger than tbe vegetative cells.
S ize. Cells -OOd-’OOS x '004-'006 mm. Heterooysts '006-
•008 X -007--009 mm. Spores -007--008 X -008--012 mm.
( Wittrock.)
Nord. & W ittr. Alg. Ex. No. 196.
Sphærozyga oscillarioides, Kutz. Sp. Alg., p. 291. Borzi.
Alg. Fico. 286.
Trichormus oscillarioides, Ealfs in Ann. Nat. Hist. 1850, p.
829, t. 8 , f. 5.
In brackish ditches.
“ I t differs from A . Thwaitesii by its more quadrate ordinary cells, and
by its smooth and elliptical heterocysts.”—Ralfs.
Plate XOIII. fig. 6. Portions of trichomes with spores and heterocysts
X 400.
Anabaena Th-waitesii. (Ralfs.)
Trichomes moniliform, straight or nearly so, joints quadrate.
Heterocysts oblong sub-quadrate, hardly exceeding the joints
in diameter. Spores nnmerous, cylindrical -with truncate ends,
very variable in length.
S ize. Cells -006--007 mm. Heterooysts -008 x -01 mm.
Spores -01--012 x -OaS-^OS mm.
Dolichospermum Thwaitesii, Ealfs Ann. Nat. Hist. 1850,
837, t. 9, f. 5.
In freshwater pools, and brackish ditcbes.
Allied to A. Smithii, but its filaments are not included in a definite
gelatinous sheath. Its filaments are also stouter, and there is a differ,
ence in the form of its cells. The heterocysts are quadrangular, and
hardly exceed in diameter the ordinary cells. The cylindrical truncated
spores are numerous, many in a chain, and variable in length, about
twice the diameter of ordinary cells.
Uncertain Species.
Anab a en a inæ q u a lis. (Ralfs.) Braun., in litt.
Forming extensive strata consisting of thick gelatinous masses
of a deep green colour.
Trichomes stout, moniliform, elongated, joints distinct, at first
quadrate, finally orbicular, with granular contents. Heterocysts
Uobose, broader than the ordinary joints, occurring at short
intervals. Spores 3-4 times longer than broad, witb truncate
ends, in chains of two to five.
Size. Not determined.
Dolichospermum inæquale, Ealfs Ann. Nat. Hist. 1850, 335,
t. 9, fig. 1.
Sphærozyga inæqualis, Kutz. Tab. Phyo. i., t. 96. Eabb.
Alg. Eur. ii., 194 ?
In boggy pools.
We have seen no specimens of this, or of Kutzing’s SfpTicerozyga
moequalis, and therefore cannot pronounce on tbeir identity. Mr. Kalfs
says th a t “ this plant forms extensive strata, composed of thick
gelatinous masses of a deep green colour. Filaments elongated, consisting
of from 100 to 200 cells, and, being stouter than in most species
belonging to this genus, visible to the naked eye. Ordinary cells distinct,
quadrate in immature specimens, but at length nearly spherical,
appearing punctate on account of the scattered granular matter which
they contain. Vesicular cells (Heterocysts) spherical broader than the
ordinary joints and occurring a t short intervals. Spores 3 to 4 times
longer than broad, with truncate ends ; in chains of from two to five
members.” May be known from A. Ralfsii by its spherical heterocysts
and catenate spores.
Plate XCIIL jig. 4.
Trichomes with heterocysts and spores X 400 ;
after Kalfs.
Genus 96. APKANIZ03MEEN0N. Morren. (1839.)
Thallus membranaceous, free swimming, bright blue, blue
green, or becoming olive. Triobomes medium size, a little
attenuated towards the apex, agglutinated parallelly and very
densely in fascicles, joints cylindrical, very closely connected,
pale blue, nearly colourless and delicately granular. Spores
elongated, cylindrical, rounded at the ends, pale blue, or somewhat
olive, exospore thin, quite smooth. Borzi Alg. Ficochrom,
p. 279.
Thuret places this genus next to Anahaena, hut, in the absence of
heterocysts, it seems that its proper place would be in Lynghyce, allied to
Oscillaria. We have retained it here, in preference to altering the “ key
to the genera,” which is given on page 221.