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behind the outer membrane, enclosing the inner one. After the fonr
cells have remained some time enclosed in the hyaline covering, this
becomes resorbed subsequently, and the four cells lie still and motionless,
but after the course of a short time the cells burst on one end by
means of an annular slit, and the apex, separated thereby from the
remainder of the cell-membrane, becomes elevated like a lid. Through
the circular opening the cell contents now emerge, which at the part
turned towards the opening is colourless. This apex moves with
vigorous motion backwards and forwards, and after an hour the cell
contents, in the form of a zoospore, leave their place ot detention, which
we now' find to be a doubly-coloured cell-membrane. The little zoospore
wheels in a lively manner about with a circling movement, whereby the
colourless point becomes directed downwards. Its appearance is like
that of an ordinary zoospore, and, like it, possesses an oval form and a
lighter apex, furnished with cilia, which during the motion is always
directed forwards. After a time the movements become faint, and
finally cease. The cilia disappear, and the light end becomes elongated
into a root, which sometimes becomes an organ of attachment, quite
like that produced in the germination of the ordinary zoospores. The
rounded end of the germinating zoospore acquires a little point-like
apex. This grow'th becomes divided by a transverse septum, and a little
two-celled OEdogonium has originated. From each spore there are thus
derived, in general, four plants.
Plate L V II. figs. 1-5. Stages in the formation of new cells—after
Pringsheim. Fig. 6, male cells of Bulhoeliæte crassa, with spermogonia.
Fig. 7, zoospore of OEdogonium—after Pringsheim. Figs. 8-10, development
of dwarf males—after De Bary. Pig. 11, spermogonia. Pigs.
12.13, imgregnation of OEdogonium ciliatum—after Pringsheim. Pig. 14,
zoospore of OEdogonium rivulare. Pig. 15, zoospore developing in its
mother-cell—after Pringsheim. Fig. 16, zoospore of Bulbochæte
setigera. Figs. 17-19, segmentation of resting spores of OEdogonium.
Fig. 20, oospore escaping from oogonium. Fig. 21, mature oospore of
Bulbochæte undergoing division. Fig. 22, four zoospores developed
from the same. Fig. 23, sterile cells of OEdogonivm Beinschii. All
maguified 400 diam.
The following is an arrangement of British species, on the basis of
Wittrook’s “ Monograph ” :—
OEDOGONIUM.
Sect. 1. Species monoecious.
A. destitute of median processes.
a Oogonia globose or subglobose.
CB. Petri, Wittr.
CE. cryptosporum, Wittr.
05. cnrvnm, Pi'ingsh.
CE. cymatosporum, W. ^ N.
CE. minus, Wittr.
CE. vernale, Hass.
CE. crispum, Hass.
CE. Tauoherii, Le Cl.
$ Oogonia elliptic or egg-shaped.
CB. urbieum, Wittr.
b. Oospores ellipsoid or egg-shaped.
CE. paludosum, Hass,
I?
B. Oogonia furnished with verticellate median processes.
a. Oospores subglobose.
OE. Itzigsohnii, De By.
b. Oospores subellipsoid.
OE. excisum, Wittr. Lund.
OE. Aroherianum. Cke. (Bringsheimianum, Archer).
Sect. 2. Dioecious species.
Sub-Sect. 1. Species with dwarf males.
A. Species n-ith dwarf males unicellular.
a. Oogonia furnished with verticellate processes in the
middle.
OE. platygynnm, Wittr.
b. Oogonia always destitute of median processes.
a Oospores globose or subglobose.
OE. Rothii, Le Cl.
OE. Aresohougii, Wittr.
OE. pluviale. Nord.
OE. undulatum (Breb.).
OE. Eeinsohii, Boy.
^ Oospores subellipsoid.
None.
B. Species bicellular, spermogonia internal, with dwarf males.
OE. depressum, Prings.
C. Species with dwarf males bùmiulticeUular, spermogonia external.
a. Oospores even.
a Oospores globose or subglobose.
OE. flavesoens, Hass.
OE. Brannii, Kutz.
OE. macrandum, Wittr.
OE. crassiusculnm, Wittr.
¡3 Oospores ellipsoid or egg-shaped.
OE. Borisianum, Le Cl.
OE. oonoatenatum, Hass.
OE. aorosporum, D. By.
OE. ciliatum, Bass.
b. Oospores eohinulate.
a Oospores globose.
OE. Cleveanum, Wittr.
OE. eohinospermnm, Br.
¡3 Ooospores ellipsoid.
None.
Sub-Sect. 2. Species dioecious, with elongated male plants.
a. Oospores eohinulate.
None.
b. Oospores smooth.
a Oogonia not, or slightly, swollen.
CB. capillare, L.
I,