I
I i ' -I
f
*
Ii
jtH
Consult Thui-et in “ Annalesdes Sciences Naturelles, Botanique,” 1843.
Walz in Pringsheim’s “ Jahrbücher” for 1866. Braun “ Eejuvenesoenoe,”
pp. 128, 140, and following.
Genus 53. VAUCHERIA. D. C. (1805.)
Characters the same as given above for the Family.
Two or three arrangements of the European species of Vaucheria have
beeu proposed, differing slightly in detail. The following is that of Professor
Nordstedt;—
VAUCHERIA.
A. Antheridia not separated from the thallus by a short empty
boundary cell.
a Tubuligee^e . Antheridia little or scarcely bent, oblong
cylindrical, or lanceolate, with an opening at the top. Bed
pigment bodies not collected in the middle of the mature
oospore, Oogonia and antheridia almost stemless.
* Oogonia nearly round.
1 7. dichotoma (L) Dimcious.
2 V. ThuretitWor. Mon^cious.
** Oogonia not round, more or less oval,
frequently rather oblique.
3. V. aversa, Hass.
4. V. sericea, Lyngb.
h COENICULAT.®. Antheridia bent in the form of a horn, or a
hook, placed on the short and bent side branches of the
thallus. Brown pigment in the middle of the mature
oospores.
aa Sessiles. Oogonia sessile (or with exceeding short
stems) beside the antheridia on the thallus.
5. V. Dillwynni, Ag.
6. F. sessiZis (Vauoh).
hh Racemosts. Antheridia at the end of a fruit branch,
which, somewhat lower down, carries the
oogonium.
* Oogonia turned upwards.
t Antheridia and oogonia bending in opposed
planes, forming an angle with
one another. When the oospores
fall they are surrounded by the
oogonium membrane, which is not
changed to slime.
7. V. geminata, Walz.
8. V. hamata, Walz.
■ft Antheridia and oogonia (mostly)
bending in parallel planes, the
oogonium membraue turns to slime
and dissolves.
9. V. terrestris, Lyngb.
** Oogonia turned-downwards.
10. V. uncinata, Kutz.
c Antheridia straight, with the top covered, and a pair of fruiting
tubes standing out at the side.
11. V. Re Baryana, Woron.
B. Between the antheridia and thallus itself is found a shorter empty
boundary cell (not containing chlorophyll).
a ANDEOPHOE.E. Several horn-shaped bent antheridia placed
on a swollen cell containing chlorophyll, which is fixed to
the side of the thallus, by means of the boundary cell.
12. Y. synandra, Woron.
S PILOBOLOIDEIE. Antheridia bordering immediately on the
boundary cell (frequently provided with several mouths).
aa Oogonium borders immediately on the thallus branch.
* Several fructification tubes on the
oogonium.
13. V, coronata, Nordst.
** Oogonium with only one fructification
opening, but the antheridia with
several,
t Oospore round.
14. F. intermedia, Nordst.
16. V. sphcerospora, Nordst.
f f Oospore lens-shaped.
16. V. piloboloides, Thur.
55 Below the oogonium a boundary cell.
17. V. Utorea, Hofm.
Place uncertain.
18. V. tuberosa, Br.
19. V. trifurcata, Kutz.
The sexual reproduction in Vaucheria has been minutely described by
Pringsheim, of which we give an abstract. Vaucheria, besides the
asexual multiplication by zoospores also exhibits a true sexual propagation,
effected by means of the two organs known as the “ hornlets” and
the spores, the latter being more correctly termed “ sporangium.” Both
organs arise like papillary branches from the tube, and in close proximity.
I t is usually the case that the papilla destined to become the hornlet is
formed sooner than that in which the sporangium originates. The two
papillae even from the first differ so widely in dimensions, that they can
scarcely be confounded. The papilla which becomes the hornlet soon
elongates into a short cylindrical slender branch, which at first rises
perpendicularly from the tube, then curves downwards until it comes in
contact with the tube, often forming a second, or a third curve, and in
this way always represents a more or less stunted branch, which frequently
exhibits several spiral turns. The papilla of the neighbouring
sporangium usually begins to appear at the time when the hornlet is
commencing its first turn ; but the period at which it arises is very
indeterminate, for it sometimes appears much earlier, whilst the hornlet
is still perfectly straight, sometimes much later after it has curved, so as
to form two limbs of equal length.
The papilla destined to become the sporangium gradually enlarges
into a considerable-sized lateral out-growth of the tube, far exceeding the
hornlet in width, whilst in length it is barely equal to the straight limb
of the latter. This out-growth which is afterwards symmetrical,
ultimately throws out a beak-like prolongation on the side looking
towards the hornlet, the rostrum of the sporangium, whence the latter
acquires its peculiar form, resembling that of a half developed vegetable
ovule. Up to this period the hornlet as well as the sporangium are not
shut off from the tube by any septum ; the cavity of the hornlet and that
of the sporangium consequently remain uninterruptedly continuous with
the parent tube, and are filled with similar contents. A number of
chlorophyll granules in an albuminous plasma and rounded oil globules,
constitute a dense lining to the tube, the sporangium, and the hornlet.
Between this and the cellulose membrane is the thin colourless cutaneous
layer.
■ f
Ij,-