NOSTOCEA. 237 
Anabaena circinalis, Phillips in Grevillea ix., p. 4, t. 184, 
figs. ¢, fy g. 
In ditches with Conferve, and floating on lakes. 
“ Floating like powdered verdigris on mountain lochs.” This species 
seems to be variable in the form and size of the spores, and in the number 
of vegetative cells which occur between the heterocysts and spores. 
Wittrock has figured varieties in which two, or even sometimes one, 
cell intervenes between the heterocyst and spore, alluding to the fact 
that in English specimens they are sometimes in juxtaposition. Al- 
though technically the Shropshire specimens would seem to belong to 
Spherozyga, yet in all other features they agree so well with this species 
that we have cited them here as abnormal forms of the present species. 
Plate XC11I. fig. 3. Portions of trichomes with heterocysts and 
spores X 400; 8, after Ralfs ; c, after Phillips. 
Anabaena Ralfsii. (Kutz.) 
Forming extensive strata of a velvety rich dark green colour, 
sometimes verging towards verdigris green. 
Trichomes moniliform, joints spherical. Heterocysts ellip- 
tical, spores elliptic or cylindrical, one or two in each series 
not contiguous to the heterocysts. 
Size. Cells 004 mm, diam. Heterocysts :005-:006 x 008 
mm. Spores ‘008-01 x ‘022-03 mm. 
Spharozyga Ralfsit (Thw.) Rabh. Alg. Eur. ii., 193. Kirch. 
Alg. Schl. 237. 
Dolichospermum Ralfsii, Ann. Nat. His. 1850, t. 9, f. 2. 
Cylindrospermum Ralfsti, Kutz, Tab. Phyc. t. 98, f. 7. 
In bogs and rivulets. 
“Distinguished from 4. inequalis by its elliptical heterocysts (which 
are comparatively less broad), by its more orbicular ordinary joints, and 
by having fewer spores.”—aljs. 
Plate XCIV. fig. 1. Trichomes with heterocysts and spores X 400 
diam. 
Anabaena Smithii. (Jhw.) Nord. F Witt. Alg. Ews. No. 197. 
Trichomes straight, each included in a definite gelatinous 
sheath ; joints subspherical, compressed, about as long as wide ; 
heterocysts subspherical somewhat barrel shaped, half as wide 
again as the joints, puncta very distinct ; spores cylindrical, very 
unequal in length, with the ends rounded and somewhat trun- 
cate. 
Sizz. Cells :004--006 mm. diam. Heterocysts 008-009 x 
‘009-0138 mm. Spores -009-"012 x :02-:04 mm. ( Wittrock.) 
Dolichospermum Smithii, Thwaites Ann, Nat, Hist. 1850, t. 9, 
f. 4. 
In boggy pools with other Alge. 
