'À
liîi
â
Filaments without a sheath distinct from
the trichome . . . . . .
(3 Filaments agglutinated in small floating
bundles . . . . .
Filaments formed of one or several coloured
trichomes enclosed in a transparent sheath,
from which the trichomes emerge to reproduce
new filaments . . . . .
Sheath containing several trichomes, at least
in the larger filaments . . . .
A. Filaments growing in scattered
creeping, erect, or floating wiok-
like bundles . . . .
B. Filaments bundled, erect, growing
in small rounded tufts, or in felt,
like tnrf of indefinite extent.
Trichomes very slender
Sheath enclosing only a single trichome
A. Filaments simple, or only exceptionally
exhibiting the beginning
of ramification where the trichome
issues from the side of
the s h e a t h .....................................
)3 Filaments agglutinated in
wick-like bundles .
B, Filaments branched. Ramifications
produced by the branching of the
trichome outside the sheath, very
irregular, and often geminate, as
in Soytonema . . . .
10 SCYTONEMEÆ
'Trichomes of which the cells
only multiply in the direction
of the length of the filament
Trichomes of which the cells
multiply as well in the direction
of the breadth of the
filament, at least where the
branches, which are always
produced by lateral multiplication,
originate
A. Cells of the triohome often geminate
or ternate in consequence
of their lateral multiplication, or
even forming transverse several
celled bands. Sheath large. Cells
surronnded with a thick membrane
very prominent in the old
filaments. Hormogones originating
in lateral branchlets formed
of a single row of cells
6 Filaments of the hormogones
much slenderer than the
principal filament, and originating
iu unilateral tnfts .
OscUlai'ia.
Trichodesmium.
A. B.
Miorocoleus.
Inactis.
A. B.
Lyngbya.
Symploca.
Plectonema.
. 11
A. B.
11
B. Trichomes formed mostly of a
single row of cells. Sheath slender.
Aqnatio plants looking like
T o l y p o t h r i x ......................................... Hapldsiphon.
( Sheaths enclosing several trichomes . . . Oystocoleus,
j Sheaths enclosing only a single trichome.
I Ramifications produced by the deviation of
the trichome, which emerges from the side
V. of the s h e a t h .........................................................................A. B.
A. Ramifications usually geminate, produced
by a fold of the trichome
which ruptures outside of the
sheath, and gives birth to two
filaments given off at a right
angle. Heterocysts scattered
here and there in the triohome
without any evident relation to
the ramifications
A Sheath very broad, forming
a transparent layer around
the trichome ,
y Filaments agglutinated in
erect wick-like bundles
B. Ramifications rarely geminate, oftentimes
solitary, and originating at
a point where the continuity of
the triohome is interrupted by
heterooysts. One or several heterocysts
placed directly above
each branohlet . . . .
'Filaments agglutinated by a
more or |less firm mucilage.
Frond nsually with a well defined
outline . . . .
Filaments free, growing in small
tufts, or forming a turf of
considerable extent
Scytonema.
Petalonema.
Symphyosiphon.
Tolypotlirix.
12 C a l o t e i c h e æ . 13
Calothrix.
13
Stigonema.
. Fischerà.
Heterooysts scattered. Ramifications very
irregular, arising from a fold in the triohome,
in the form of a V, where originate
two geminate filaments, distinot at the base,
but at a certain height transformed, for the
greater part, into a single filament, composed
of a single row of cells. Frond hollow, but
hard, folded aud looking like a little Bivularia
................................................................
Heterocysts basal (placed at the base of the
principal filaments and branchlets). Ramifications
produced by the transverse division
of the trichomes, the upper part of which
detaches itself and becomes a lateral branch-
let, while the lower part extending itself by
the side of its old tip makes a new extremity
b similar to the f i r s t .....................................
Hormactis.
14