w
Hydiodictyon u tx ic u la tum . Both. Babh. Alg. 66.
Size of the families (net) variable ; also of the cells (forming
the meshes) and the gonidia, according to circumstances.
Eng. Flora v., p. 359. Harv. Man p. 140. Eng. Bot. (Ed.
2) t. 2504. Hook. Soot ii. 80. Gray. Arrang. i., p. 300. Hass.
Alg. 225, t. 58.
Conferva reticulata, Dillw. Conf. t. 97. Eng. Bot. (Ed. 1)
t. 1687. Huds. Ang. ii. 596. Relhan Cant. 444. Hull Br.
FI. 331. Abbot Bedf. 275. With. iv. 132. Ray Syn. p. 59.
Dillen. Muse. 20, t. 4, f. 14.
In clear water.
For the development of this species see remarks under the genus, and
also an elaborate account in Braun on K-ejiivenescence, pp. 137, 171, 190,
197, 222, and 261. Observations by Cohn “ Der Mikroskopischen Algen
und Pilze,” p. 109, and Pringsheim “ Dauersohwärmer des Wassernetzes
” (Berlin, 1861).
Plate X IV . fig. 1. a, “ Water net,” natural size ; h, one of the
” meshes ” magnified ; o, cell with microgonidia X 300, after Cohn; d,
portion of cell with angular macrogonidia X 300, a fte r Cohuj e, free
macrogonidia j /, active macrogonidia X 600.
I*
Sub-Family 6 . O ph io o y t iea i.
Cells cylindrical, unsequipolar, at first short, then elongated,
either variously curved and contorted, sometimes circinate, one
or other pole attenuated into a thin, short stem, free swimming ;
either straight or more or less curved, collected in an umbel with
a simple stem, or being repeated, forming a composite umbel.
Cell-contents parietal, homogenous or granular, green, sometimes
mixed with scattered reddish or brownish globules. P ro p ag a tion
by gonidia.—RaVh. A lg . E u r. iii. 66.
¡1
Genus 27. OPHIOCYTIUM. Nag. (1849.)
Cells cylindrical, at first short, then elongated, variously
curved, sometimes circinate, attenuated at one extremity into
a short, thin stem ; free swimming. Propagation by division
of cell-contents and formation of gonidia.
Rabenhorst unites the iollowing genus with the present, giving to it
the characters of the sub-family, bnt we have preferred to follow A.
Braun and keep them distinot.
Ophiocytium co ch lea r e . Br. Alg. Unic. p. 54.
Slender, pale green, often very long, filiform, variously curved,
circinate, or more or less loosely spirally involved ; stem short,
spine-like, acute or truncate ; contents homogeneous.
S iz e . Cells •005--0075 mm. diam .; length variable.
Archer, Micr. Journ. 1866, p. 63. Rabh. Alg. iii. 67.
Ophiocytium, “ Science Gossip,” June, 1867, p. 127, fig. 103.
In pools, mixed with other algte.
Plate X IV . Jig. 2. a, young cells; c, older cells ; I, mature cell X
400.
G en u s 28. SCIABIUIHC. Braun. (1855.)
P lan t from a single individual producing a family. Thallus
(solitary) adnate, unicellular ; cell elongated, cylindrical,
straight, attenuated at the base into a slender stem. Gonidia
about 8, resulting from division of the cell-contents, at length
protruding from the ruptured apex, retained at the mouth and
extending in the form of an umbel, each individual becoming
developed into a cylindrical cell like the mother-cell. This process
is repeated to a third, or sometimes a fourth generation,
forming a composite or decomposite umbel. Ultimate cells
producing free biciliate zoogonidia.
The cylindrical cell of Soiadmtn possesses uniformly distributed green
contents, which are interrupted, in perfectly developed cells, by light
cross streaks, and are divided into a row of 5 to 8 about equal masses,
which become gonidia. I could not detect nuclei in the individual seg-
ments of the contents passing into the formation of gonidia.—Braun
Rejuvenescence, p. 260.
Sciadium a ib u scu la . Braun Unicell. Alg. p. 106, t. 4.
Umbellate. Cells stra ig h t (rarely falcate), obtuse at the apex ;
stem about as long as the diameter of the cells.
S i z e . Cells '0038 mm. (rarely '007 mm.) diam.
Sciadium arbuscula, Mior. Journ., 1866, p. 4. Archer, Micr.
Journ. xii., 1872, p. 314.
Ophiocytium arbuscula (Br.), Rabh. Alg. Eur. iii. 68.
Attached to confervoid algas and aquatic plants.
Braun, writing of this species, says—“ I t displays an originally obovate
tube, generally becoming elongated into a cylindrical form, obtuse
above, and prolonged into a slender attached pedicel below. The contents
consist of uniformly green mucilage, in which a small vesicle
may sometimes he distinguished, hut only in the earliest stage of growth.
The pedicel is transparent and colourless, and secretes at its base an
originally yellowish brown, afterwards dark brown mass, which gradually
expands into a disc-shaped foot. When the growth is completed the
green contents become divided into several masses, developing into a
series of 6-8 germ cells ; the cell membrane dehisces, throwing off its
summit as a finger-stall.shaped cover, bnt the germ cells, instead of
leaving the open tube, all collect at the point of exit with their inferior,
narrower, and somewhat pedicellately elongated ends sticking in the
tube. Thus is produced a capitule, and by the advancing growth of the
young family an umbel formed of individuals exactly resembling the
parent individual from which they originated. The emptied mother-oell
tube remains as the stem and support of the umbellate family, and
gradually becomes filled from above downwards with the same yellow and
reddish brown secreted substance which it exhibits at its own base. The