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plete the process. The union of the two cells appears to take place in
several ways. In accordance with one plan, connecting tubes, pushed
out from near the ends of the cells, grow for a short distance nearly at
right angles to the long axis of the filaments, and then bend at a right
angle to themselves, so as to run parallel to the filament cells. The ends
of these processes are, of course, opposed to one another, and coming in
contact, fuse together so as to form a continuous tube for the passage of
the endochrome. Another method by which neighbouring cells are
sometimes connected is by the formation of ooadjacent pouch-like enlargements
of the opposing ends, and a subsequent fusion of these
newly-formed enlargements by the absorption of the end wall between
them."
“ There is still another method of conjugation, the so-oalled genuflexuous,
in which, instead of a connecting tube being formed as the medium
of union, two cells of opposing filaments become sharply bent backwards,
so that their central portions are strongly thrust forward as
obtuse points, which, coming in contact, adhere, and allow of a passageway
between the cells being made by the absorption of their cohering
walls.”—TTooif’s F. Wate7-Algce, p. 161.
Hassall says that the conjugation in Zygnæmaceoe results in the production
of “ a dark body, of either an oval or circular form, and enveloped
in membrane, which Vaucher, Decaisne, and Jenner regard as
the true spores, but which Agardh declares resolve themselves after a
time into zoospores, an opinion in which I concur, applying the term
sporangia to them.” I t need scarcely be added that this view is erroneous,
the resulting body germinating direct after a period of rest, and
termed a zygospore.
The same author makes also another statement, rather vaguely stated,
which is not confirmed by experience. “ I t is curious to remark that
the cells in one part of the same filament will part with their contents
and remain empty, while in another they will be the recipients of the
contents of the cells of another filament.” His remarks on agamse-
sporons Conjugatoe will be illustrated under the sub-family Gonatonemeæ.
Sub-Family 1. Ztgnsmeæ.
Cells cylindrieal, united in threads. Zygospore undivided,
and mostly contracted, passing into the resting condition, afterwards
developing into a germ-cell, divided into a basal cell, and
a thread-cell, capable of division.
As hereafter explained, this sub-family differs from the Mesooarpeoe
chiefly iu the development of the spore, which is not surrounded, or
accompanied, by two to fonr deoidnons lateral cells.
G en u s 44. Z Y G N E M A . Kutz. (1843.)
Cells with two axile many-rayed chlorophyll bodies standing
near the central cell nucleus, each containing a starch-granule,
or quite filled with dense granular contents, surrounding two
starch-granules lying near th e centre, (a ) zygo.spore in the
bladdery middle space between the ladder-like united pairing
cells (i)) copulation ladder-like, or lateral between two cells
of the same thread.
I n certain of the species of this genns the zygospores are produced iu
the conjngating canal, and in other species in one or other of the conjugating
cells. This fact is taken advantage of in the following arrangement
:—
A, Zygospores produced in conjugating canal.
* Sporodeimi scrobiculate.
1. Zygnema pectinatum, Ag.
** Spoi'oderm even.
2. Zygnema Ralfsii, Kutz.
3. Zygnema parvulum, Kutz.
B. Zygospores produced in one or other of the conjugating cells,
* Sporoderm punctate.
4. Zygnema cruciatum ( Vauch.).
5. Zygnema stellinum (Vauch.).
6. Zygnema Yaucherii, Ag.
7. Zygnema anomalum (Hass.).
** Sporoderm even.
8. Zygnema leiospermum, De Bary,
9. Zygnema insigne, Kutz.
A. Zygospores produced m conjugating canal.
Z y g n em a p e c tin a tu m . Ag. Syst. p. 78.
Sterile cells 1-2 times as long as broad.
Zygospore globose or broadly elliptic, dark olive, sorobicu-
late, formed in tbe canal of conjugation.
Siz e . Cells 'OS-'OSS mm. diam. (sometimes less), zygospore
•04 mm. diam.
D eB a ry Conj. p. 77, t. 1, f. 1 5 ; 19, t. 8, f. 13. Gray
Arr. i. 1296.
Conjugata pedinata, Vaucb. Conj. p. 77, t. 7, f. 4.
Conferva Mpunctata, Eng. Bot. t. 1610.
Conferva decussata, Dillw. Conf. Syn. p. 5, (?)
Ztjgogonium pectinatum, Eabh. Alg. iii., 252. Kirsch. Affi.
Schl. p. 126. ®
Tyndaridea conspicua, Hass. Alg. t. 39, f. 1, 2, Ann. Nat
Hist, xii., 187, t. 7, f. 17.
Tyndaridea immersa, Hass. Alg. t. 89, f. 3. Ann. Nat. Hist,
xii. 188, t. 7, f. 19.
Tyndai'idea decussata, Hass. Alg. t. 89, f. 6. Ann. N. Hist
xii., 188, t. 7, f. 18.
Zygogonium conspicuum, Kutz. Tab. v. t. 12, f. 2.
Zygogonium immersum, Kutz. Tab. v. t. 12, f. 5.
Zygogonium decussatum, Kutz. Tab. v. t. 11, f. 4.
Tyndaridea pedinata, Eng. El. v. p. 361 ; Eng. Bot. ii. t.
2597, Harv. Man. 142 ; Mack. Hib. 231.
Zygnema bipunctatum, Grev. El. Ed. 320 ; FI. Devon, ii. 50.
In still waters.
As noted above, we include here three of Hassall’s species of Tyndaridea.
Kirsohner does the same, with the addition of Kntzing’s Z ano-
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