a Spores measuring -004 x -008 mm. or more.
1. Sheatlis confluent, trichomes scattered,
irregularly interlaced.
* Spores rounded oval . . 10. collmum.
** Spores oval . . . .1 1 . muscobum.
2. Sheaths well defined, and separable
by pressure, trichomes folded vertically
and parallel . . .1 2 . Passerinianum.
i8. Spores measuring -004 x -006 mm. or more.
* Mucilage tolerably firm ; trichomes
olive. Spores oval . 13. HüMiEUSUM.
** Mucilage soft, easily diffluent,
trichomes æruginous green.
Spores subglobose . . .1 4 . caldcóla.
B. Fronds deformed, hollow ; joints spherical
compressed 15. foUacmm.
IV. Communia. Terrestrial species (sometimes inundated). Fronds at
first globose, then becoming tongue-shaped, plane, or irregular not
adherent. ’
Adult frond suborhioular, folded, undulate,
entire or lobed, often perforated ; joints
spherical-compressed, uniform. . .1 6 . commune.
V. Sphæbica . Fronds globose or subglobose (often becoming irregular
when they grow large), limited by a firm and resisting perideimio
coating.
A. Terrestrial speoies, or sometimes inundated.
a Trichomes not fusiformly swollen between
the heterooysts.
1. Fronds attaining 1 m. and more.
Trichomes torulose.
* Frond firm, trichomes com-
pact, joints oask-shaped, or
compressed sphærical close together,
uniform ; spores oval,
smooth . . _ . . .1 7 . SPHÆBICUM.
Fronds soft, trichomes much
spaced out, of unequal size,
joints nearly sphærioal, sheaths
often coloured, contrasting
with the generally unooloured
mucilage ; spores oval, smooth 18. eu pe sx b b .
2 Fronds very small, punctiform, not
attaining 1 mm,
Trichomes large; joints cylindrical,
a little constricted at the
point of junction ; spores globose,
smooth . . . .
P Trichomes fusiformly swollen between
the heterooysts ; joints dissimilar, the
one kind straight and elongated, the
other larger and sphærical ; spores
sphærioal, r o u g h .....................................
B. Aquatic species (colour blue, or approaching
to blue).
a Trichomes dissimilar, unequal ; joints
of two forms, the one (young) elongated,
the other large, sphærical, often
19. MACBOSPOBUM.
20. sphceroides.
filled with opaque granules . . .2 1 . CCEBULBUM.
P Trichomes homogenous, regular.
1. Frond very small ; trichomes very
c o m p a c t 22. minutissimum.
2. Frond attaining 2-10 mm.
* Joints sphærioal, compressed . 23. gregarium.
** Joints discoid, very compact . 24. edvie.
3. Fronds attaining the size of a nut 25. pbunieobmb.
VI. Vebbucosa. Aquatic species. Fronds rounded or discoid, at first
full, then hollow, limited a t the circumference by a firm and tough
periderm. Trichomes thin, very regular, spaced out and a little
flexuous at the centre, more compact, and very distorted at the periphery.
a. Fronds subglobose or warted. Mucilage
tolerably soft. Trichomes medium compact,
and often deprived of sheaths at
26. V B B E U C O S U M .
the periphery . . . .
h. Fronds at first discoid or tongue-sl
a little ovoid, hard ; trichomes radiating
regularly from the centre to the circumference
and there forming a very dense
l a y e r .........................................................27. parmelioides.
VII. Zbtteestbdtiana. Aquatic species. Fronds sphærioal, hard,
tuberculose, divided into radiating separable
lo b e s ...........................................................................28. Zetterstedtii.
VIII. Flagbumeobmia. Terrestrial speoies. Fronds forming thongs,
linear straight, and very long.
Frond linear or setaceous, subdichotomous
trichomes longitudinally parallel . . 29. Jlagelliforme.
I . I ntricata. S p e c ie s a q u a t ic , f r o n d s so ft, g e la t in o u s w ith o u t
d e te rm in a te f o rm , often f lo a t in g .
N o s to c I i in c h ia . (Both.) Born ^ Thur. Notes Alg. p. 86, t. 28,
/ . 1-12.
Fronds lobed, multipartite, free swimming, as large as a
■walnut, lobes elongated and anastomosing, æruginous green, at
length becoming brownish.
Trichomes flexuous, aggregated, joints short and close,
sphærioal, or sphærical compressed, sheaths nncoloured, very
refractive. Heterocysts slightly oblong. Spores subglobose or
oval.
S iz e . Join ts ’0085 mm., heterocysts ’005-'006 mm. diam.,
spores (in form in t r ic a tum ) subglobose -0065 x ‘0U9 mm.
R i v u l a r i a L i n k i a , Roth. Neue Beitr. p. 263.
N o s t o c c o n fu sum , A g . Syst. A lg . p. 22.
M o n o rm ia in t r ic a t a , Berk. Glean, t. 18 . Hass. A lg . 286, t.
7 5 , f. 1 1 . Ra lfs. Ann. Nat. Hist. 18 5 0 , p. 326, t. 8, f. 1 .
A n a b a e n a in t r ic a t a , Ku tz . Phyc. Germ. 1 7 1 . Rabh. A lg .
Eur. ii., 18 3 .
A n a b a e n a J lo s -a q u c e , Rabh. A lg . Sachs. No. 27.