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F a m i l y VI. ULOTRICHBÆ.
Algæ growing either in fresh water ( Dlothrix), or marine or
sub-marine {Hormiscia), or terrestrial {Bormidium, Schizo-
gonium), either of a bright green or yellowish green colour.
Threads very shortly articulate, simple, very rarely dividing into
single branches, free, now and then laterally connate in bands
{Schizogonium).
Primitive cells always many times longer than their diameter,
after repeated division equal, or shorter (rarely a little longer),
all fertile. Oell-membrane either thin {Ulothrix, Bormidium)
or thick, sometimes very thick, and distinctly lamellose {Hormiscia).
Cell-contents at first effused, parietal, including a
starch granule, after simple or repeated division transmuted
into gonidia.
Gonidia of two kinds, Macrogonidia sphærioal, ovoid, or
ovate-oblong, rounded at one pole, and acute at the other, furnished
with 2 or 4 vibratile cilia, often germinating in the
mother-oell without sexual fertilization. Microgonidia much
smaller, of similar form, furnished with two cilia at one extremity.
Both kinds of zoogonidia produced within the cells of
the threads, emitted either by a poriform opening in the mothercell,
or by the splitting or breaking up of the mother-cell.
For detailed information on this family consult Braun’s “ Eelnvenes-
cence” (Ray Society), pp. 148, 161, 184, 208, 223 ; Dr. A. Dodel, “ die
Kraushaar-Alge,” Ulothrix eonata, in Pringsheim’s “ Jahrbücher ’’ t. x. •
Cienkowsky “ Zur Morphologie der Ulotrioheen ” (1876) ; Thuret, in
“ Ann. des Sciences Naturelles,” xiv. (1850), p. 222 ; and Dr. Braxton
Hicks, in “ Quarterly Journal of Mioroscopioal Science,” 1861, p. 157.
Genus 66. HORMISCIA. Ares. (1866.)
Articulate thread fixed by the basal cell, which is attenuated
downwards; simple, or now and then emitting branchlets.
Cells abbreviated, enclosed by a thick cell-membrane, which is
often manifestly lamellose. Cell-contents green, parietal,
including an amylaceous granule.
Propagation by macrogonidia and microgonidia.—Rahh.
A lg . E u r. iii. 361.
The filaments are sometimes cylindrical, sometimes tornlose like a
rosary, m consequence of the barrel-like inflation of the separate cells •
sometimes stretched ont, sometimes frilled and interlacing each other,
with a reiatively thicker stratified membrane. Vegetative or asexual re^
production is effected by maorozoospores, which originate 1-4 in a cell
and after becoming covered with a transparent bladder make their exit
through an opening formed iu the lateral wall of the mother-oell. The
macrozoospores are of a thick, short, pear-shape, furnished with four
oiha, a coloured spot, and a contractile vacuole. After a time they
come to rest, and fixing themselves by the mouth en(l,.they lose their
oilia and envelope themselves in a membraue. The fixed end developes
into a root-like, colourless organ of attachment; tbe free end growing
into a club-shaped plantlet, through the cell, dividing into two by a cross
partition, and each of these again iu two, and so further. Sexual reproduction
arises throngh repeated bipartitioii in each cell, from 8-32 and
more, smaller microzoospores being produced. They have only two
oilia, and after a swarming for a time they conjugate laterally in pairs,
forming a zygospore, which attaches itself by the end corresponding to
Che mouth of the miorozoospore. I t grows very slowly, and finally
breaks up by the simultaneous division of its plasma into 2-14 swarmspores,
W'hich oonstitnte the beginning of a new sexual generation. If
any of the microzoospores remain behind in the mother cells, they are
able, without copulation, to germinate and grow into independent plants
which may be seen singly or in groups projecting from the mother,
cells.
H o im is c ia m on ilifo rm is. {Kutz.) Rabh. Alg. Eur. i l l . ,361.
Pale green, more or less críspate, often mixed with other
Alg» ; colls equal or a little shorter than their diameter ; oell-
membrane thick, colourless, somewhat lamellose, more or less
constricted at the septa.
S i z e . Cells 'O ll-'O ld mm. diam.
Ulothrix moniliformis, Kutz. Tab. Phy. ii., t. 88. Kirch Ale.
Schl. p. 76. ^
In swamps, amongst Sphagnum, &c.
Plate L X X . fig. 1 . Portions of threads of Hormiscia moniliformis
X 400 diam.
Horm iscia zona ta . {Web. If M ) Aresch. Obs. p. 12.
More or less bright green, mucous, two or three feet long,
often less, either floating or interwoven, sterile cells equal, or
half their diameter ; fructiferous cells usually a little longer
than bro ad ; cell-membrane thick, slightly oonstrioted at the
septa.
S i z e . Cells •012-'04 mm. ; macrozoospores '012-'018 x '01
•012 mm. ; microzoospores •005--01 x-004--007 mm.
Eabh. Alg. Eur. iii., 862.
Ulothrix zonata, Kutz. Tab. Phy. ii., t. 90, f. 2. Kiroh. Alg.
Schl. p. 76. Dodel in Prings. Jahrb. t. x., pi. i.-vin.
Lyngbya, zonata, Hass. Alg. 220, t. 59, f. 1-6.
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