! t
I
F a m i l y YIII. OHÆTOPHORAOBÆ.
Aquatic or swamp-living algæ, rarely terrestrial, monoecious
or dioecious. Articulate filaments varions, often dicliotomously
branched, not rarely fasciculately branched, accumulated in
tufts or pulvinukjs, nestling in a somewhat fluid or firm gelatinous
mucus, or constituting, for the most part, a filamentose,
rarely a somewhat foliaceous thallus (formed from a single
stratum).
Propagation by oospores after sexual fecundation, or by zoogonidia
; the latter produced singly, or by the division of the
cytioplasm, or contents of the sporangium, into eight or sixteen.
G e n u s 70. MICROTHAMNION. Nag. (1849.)
Articulate filament dichotomously or trichotomonsly branched,
now and then very much branched, straight, with the terminal
cell obtuse, or nearly so, afterwards swollen, forming a sporangium.
Cell contents effused, containing scattered amylaceous
granules. Propagation by zoogonidia. Plants microscopical,
more or less with a gelatinous investment.
Micxothamnion v e x a to i. CJee. in Qrevillea xi., p. 75.
Filaments erect, very slender, dichotomously branched, more
or less growing in tufts. Cells cylindrical, longer than broad,
not at all constricted at tbe joints, dissepiments scarcely visible.
Cell membraue thin, pellucid.
S i z e . Cells about -003 mm. diam.
Attached to aquatic plants in clear springs, &c.
A very delicate plant, first found by Mr. Turner in Yorkshire, and
since detected iu several localities in England. Very much more slender
than M. strictissimum.
Plate L X X I II . Jig 1. Filaments of Microthamnion vexator X 400.
a, tufts of plants natural size.
G e n u s 71. STIGEOCLONIUM. Kutz. (1843.)
Articulate threads simply branched, branches and branchlets
scattered, rarely approximate in a fasciculate manner, acute at
the apex, sometimes attenuated into a colourless bristle, at times
extended very long, at other times furnished with shortly
subulate branches. Cell membrane very thin and hyaline, homogeneous.
Cell contents with th e chlorophyll arranged in
transverse bands.
Propagation by oospores or zoogonidia, the latter formed by
division (4-16) of the cell contents, e a c h zoospore furnished with
a red parietal spot and fonr vibratile cilia.
S tig e o c lo n ium th e rm a le . Braun in Kutz. Spec. p . 352.
Bright green, very much branched in a fasciculate manner,
somewhat creeping at the base, filaments and branches attenuated
upwards to the cuspidate apex, branchlets for the most
part alternate, rather remote, nearly erect or somewhat divei-
gent, setiform, joints variable in length, at the base of the
filaments equal or twice as long as the diameter, becoming
turgid, in the upper part of the branchlets 3-5 times as long as
the diameter ; chlorophyllose bands broad, sometimes effused.
S i z e . Cells -012 mm.
Eabh. Alg. Eur. iii., 376. Kutz. Tab. Phyc. iii., t. 2, f. 4.
Draparnaldia elongata, Hass. Alg. 123, t. 10, f. 3. Ann.
Nat. Hist. Aug. 1842, xi., p. 4.
In thermal springs, &c.
Hassall found this speoies on one occasion growing in a horse-trough.
I t is sometimes mixed with other algse in ditches.
Flate L X X I II . fig. 2. Filament of Stigeoclonium thermale with
zoogonidia X ^00 diam.
s t ig e o c lo n ium te n u e . Ag. Syst. 57.
Bright green, lubricous ; filaments a little branched, branches
nearly simple, cells equal or 2-3 times as long as their diameter,
more or less distinctly constricted; chlorophyllose bands
narrow : branchlets scattered, shortened, nearly erect, subulate;
cells at the base longer than broad, abbreviated towards the
apex.
S iz e . Cells *01 mm. diam.
Kutz. Tab. Pbyc. iii., t. 3, f. 1. Kabh. Alg. E u r. ill., 377.
tenuis, En g . F l.v ., o ' / t ^ l l '
Harv. Man. 122. Mack. Hib. 222. Hass. Alg. 123, t. 11,
Conferva lubrica, Dillw. Conf. t. 57. Grev. Fl. Ed. 318.
Hook. Fl. Soot, ii., 82. Gray Arr. i,, 303.
Conferva exigua, Dillw. Conf. t. 2 (young).
In streams and ditches.
“ At first the filaments are enclosed, in the manner of a Chcetophora,
in a common somewhat definite gelatine; afterwards, on its buisting,
they issue from it like a Conferva, but are at all times very gelatinous.
—Harvey.
Plate L X X I II . fig. 3. Filament of Stigeoclonium tenue X 400 diam.
- I