vesicle Avlucli attains the thirtieth of a millemetre in length.
I t is entirely invested with cilia, rather short, the vibration
of which determines the advancing movement of the spore,
hi. Unger first pointed out these organs in a great and curious
work recently published.* The interest of the subject,
and the facility of procuring each day fresh specimens, from
January until May, determined me to study th a t plant with
care. I proceed to give the result of my observations.
The tufts of the Vaucheria ( V. clavata) are formed of a
network of filaments, cylindrical, branched, continuous, which
enclose the green granules (endochrome) and colourless mucilage.
A t the period of the formation of the spore, the
extremity of its filaments swell up in the form of a club, and
the green matter becomes there condensed, so as to assume a
blacîdsh tint. (See Plate I I . / y . 21, 22.) Near the base of
the enlargement the granules are seen separated the one from
the other, leaving an empty space as if the mucdage had
condensed itself in its turn, and driven the granules above
and below. This displacement continues until the endochrome
forms well-defined lines on each side. (See Plate I I .
Jig. 23.) Then the great change takes place, Avhich consists
in the operation which Ave are about to describe, viz. the
separation of the mother plant and of the reproductive body,
subsequently clothed with a membrane proper to itself
(epispore), possessing a distinct organization.
Although this phenomenon continues but for a few
minutes, it is easy to observe It, since the movement of the
granules is almost insensible. Moreover, the separation is
not discontinued after the first time. I have seen the
operation thrice repeated upon the same filament.
The spore then takes the form of fig . 24., th a t of an elongated
oval vesicle, Avhose two divisions are nearly black by
the condensation of the endochrome, the inferior division
containing much less endochrome. I t is then tha t the crisis
approaches: the superior extremity suddenly becomes protruded,
the granular fluid empties itself into the protruded
* Die Pflanze in Momente der Thierwerdung. AVien. 1843.
portion Avhieh quickly increases in volume, so tha t the opposite
extremity becomes separated from the filament. A t the same
time the spore commences to tu rn on its great axis in such a
manner, as that all the granules Avhich it contains are seen to
pass rapidly from right to left, and from left to right, as
though they moved in the interior of a transparent cylinder.
The operation by which the spore endeavours to escape
occasions a very marked contraction ; hut in some fcAV
instances it succeeds in disengaging itself, and springs with
rapidity into the surrounding liquid. The colourless part,
which corresponds to the beak, is always directed in advance.
The spore does not cease to turn upon itself, but its progress
Is somewhat regular, quicker or sloAver in one direction or
another ; in general, it quickly reaches the edge of the glass as
though it tried to escape ; sometimes it stops ; then in an
instant afterwards It resumes its course. The epispore from
which the cilia proceed describes a large granular areola.
As to the cilia themselves, they are invisible by reason of the
rapidity of their movement ; but we may judge Avell of their
action by putting the spore in an infusion of carmine, indigo,
or gum water, &c. Nothing is more curious than to follow
its progress in a strong infusion of carmine for example.
The coloured granules through which the spore makes its Avay
are driven with force by the motion of the cilia; a rapid
current is established on each side of the spore, and a long
track is described after it. When it meets with an obstacle,
such as the filaments of Zygnema or Vaucheria, it becomes
deformed (or is put out of proportion) ; but the motion of the
cilia is not arrested. I t is also the same Avhen it is compressed
even to the extent of producing the extravasation of
the endochrome ; the vibration of the cilia continues in the
part not injured. I have observed many times the emission
of the spore in a coloured infusion, and then noticed that the
agitation of the granules by the motion of the cilia is not
felt until about a fourth part of the spore has been released.
I t is necessary, in order the better to see the cilia, to
arrest them by means of some reagent, such as opium, iodine,
the proto-nitrate of mercury, &c. The effects of the Avatery
c