238 NEMATOGENZ. 
“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 species of Dolichosper- 
mum. The ordinary cells are subspherical, somewhat compressed, and 
of less diameter than the heterocysts, which are barrel-shaped, and 
with very distinct 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 XCIII. fig. 7. Portions of trichomes with heterocysts and 
spores X 400; fig. a from Scandinavian specimens; fig. b from British 
specimens. 
Anabaena oscillarioides. Bory. Dict. Hist. Nat. 
Forming a bluish green stratum. 
Trichomes elongated flextous, joints subquadrate, distinct ; 
heterocysts barrel-shaped or elliptic. Spores oval, catenate, 
somewhat larger than the vegetative cells. 
Sizp. Cells 004-005 x :004--006 mm. Heterocysts -006- 
‘008 x ‘007-009 mm. Spores :007--008 x :008-'012 mm. 
( Wittrock.) 
Nord. & Wittr. Alg. Ex. No. 196. 
Spherozyga oscillarioides, Kutz. Sp. Alg., p. 291. Borzi. 
Alg. Fico, 286. 
Trichormus oscillartoides, Raifs in Ann. Nat. Hist. 1850, p. 
329, t. 8, £5. 
In brackish ditches. 
“Tt differs from A. Thwaitesii by its more quadrate ordinary cells, and 
by its smooth and elliptical heterocysts.”—Ralfs. 
Plate XCIII. fig. 6. Portions of trichomes with spores and hetero- 
cysts X 400. 
Anabaena Thwaitesii. (Raljs.) 
Trichomes moniliform, straight or nearly so, joints quadrate. 
Heterocysts oblong sub-quadrate, hardly exceeding the joints 
in diameter. Spores numerous, cylindrical with truncate ends, 
very variable in length. 
Sizz. Cells 006--007 mm. Heterocysts ‘008 x ‘01 mm. 
Spores ‘01-012 x :025-:03 mm. 
Dolichospermum Thwattesii, Ralfs Ann. Nat. Hist. 1850, 
8387, t. 9, £. 5. 
In freskwater pools, and brackish ditches. 
Allied to A. Smithii, but its filaments are not included ina 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. 
Plate XCJI1I. fig. 5. Portions of trichomes with heterocysts and 
spores xX 400. 
