Genus 112. HHAAFFAAII..OOSSIIPPHHOONN.. Nag. (1840.)
Trichomes formed mostly of a single row of cells, sheath
slender. Aquatic plants, looking like Tolypothrix.
Hapalosiphon b y sso id eu s. Kirch. Alg. Schl., 231.
Tufts compact, dark olive, trichomes ascending, rigid, olivaceous,
sparsely branched, containing cells arranged in a single
series. Cells at first rounded quadrate, equal in length and
breadth, becoming when older divided and shorter, one-third or
nne-fonrth the length of their diameter ; sheath very thick,
distinctly lamellose, golden yellow, attenuated and obtuse at the
apex.
S i z e . Trichomes - 0 2 5 - - 0 3 mm. diam. Cells -0 1 2 x -0 1
mm.
Sirosiphon truncicola, Rabh. Alg. Eur. ii., 286. Hedwigia
i., p. 47, t. ix., f. 3.
Hassallia byssoidea, Hass. Alg. 232, t. 67, f. 5.
Scytonema byssoideum, Harv. Eng. Fl. v., 366. Berk. Glean.,
t. 19, f. 1. Harv. Man. 156.
On trnnks of beech, &c.
Plate CXI. fig. 5, Portions of triohomes X 400 diam.
S P E C IE S FO R E N Q U IR Y .
Dasy g lo ia amozpha. Thwaites.
Gelatinous, amorphous, sheaths of the trichomes thick, mucilaginous,
cohering, slightly branched ; internal trichomes blue-
green, slender, simple, septate.
S iz e . Not indicated.
Dasygloia amorpha, Thwaites in Eng. Bot. ii. Supp., t.
2941.
In bogs.
Coalescing in a solid gelatinons mass, as large as a swan’s egg. The
filaments, quite at the base of the plant, have rather a membranous
than gelatinous sheath, and closely resemble those of a Lyngbya, in
consequence of which the base of the mass is green, but in the centre of
the plant each filament is furnished with a very thick colonrless gelatinous
sheath, which is firmly coherent with those in contact with it.
Towards the periphery of the plant these sheatlis assume a brown
colour, and become somewhat separate and distinct, rendering the surface
shaggy. Occasionally the tips of the filaments are wound spirally
round the portion beneath them.
Plate OXXI. f ig .l . a, portion of gelatinous mass, natural size; b,
threads, with gelatinous sheaths, magnified ; c, portion of triohome, with-
out sheath, further magnified—all after Thwaites.
Petzonema fzu ticu lo sum . Thwaites.
Plants densely cæspitose, erect, somewhat regularly branched,
branches free, with obtuse rounded apices, and each with a
heterooyst at the base. Endochrome annulated, increasing in
diameter towards the apices of the filaments.
S iz e . Fronds -2 mm. long, triohomes '004 mm. diam.
Petronema fruticulosum, Thwaites, Eng. Bot. ii., Supp., t.
2959.
Scytonema crustaceum, Ag. Syst., p. 39 (fide. spec, in Herb.
Hook.).
On rooks. Winter.
“ Forms a frustulose areolated olive brown crust upon the wet per-
pendicular surface of limestone rocks, to ■which it adheres so slightly as
to be very readily detached. The plants are densely crowded in little
hemispherical masses, which, together, produce the peculiar areolated
appearance of the crust. Each separate plant consists of a single filament
at the base, which is from 1-4 or even more times tri- or tetra-
cholomously branched, and thus a furticose habit is given to the species.
Each branch has a connecting cell at its base, and sometimes one also at
about the middle of its length. The very thick cartilaginous sheaths are
of a pale brown colour towards the base of the plant but darker upwards,
except at the apices, which are frequently nearly colourless. The
endochrome is of a dull green colour, extremely narrow, and indistinctly
annulated; towards the ends of the filaments, however, it becomes
much wider and slightly moniliform.”
There is in the Kew Herbarium (Herb. Hookerianum) a specimen of
Scyto7iem(i critstaceum, Ag., received from that authority himself—the
name written by him, which is clearly identical with Thwaites’s plant, but
it could not consistently be united either with Scytonema or Stigonema,
hence we have retained the name applied to it by Thwaites and placed
it here, subject to further investigation, its immediate allies being at
present doubtful.
Plate CXII. Jig. 2. Petronema frutionlosum after Thwaites; fig. 3,
Scytonema crustaceum X 400, from authentic specimen received from
Agardh.
Sub-Tribe II. TRICHOFHOREÆ. Filaments tapering at the toy
into a hyaline hair.
F a m i ly IV. CALOTRICHEÆ.
Filaments free, or agglutinated into a definite thallus, te rminating
at the apex in a delicate hair-like extremity. Heterocysts
normally present, scattered, or basal.
Genus 113. CALOTHRIX. Ag. (1824.)
Trichomes rather rigid, straight, attached, often fasciculate;
growing in small tnfts, or forming a turf of indefinite extent.