The English flora - SeaweedAfrica

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362 ALG.fc CONFERVOIDE^:. [Zygnema.
70. Zygnema. Ag. Zygnema.
Filaments articulated, simple, finally united by transverse
tubes. Endochrome forming dotted, spiral rings, which, after
conjugation, are condensed into a globule in one of the filaments.
Name, Zyyos, a yoke, and r^u, a thread; aptly expressive of
the curious conjugation of the filaments.
1. Z. nitidum, Ag. (shining Zygnema); filaments dark-green
parallelly joined, articulations with numerous arching spires.
Ag. Syst. Alg. p. 82. Conferva princeps, Vauch.— C. nitida,
Dillw. Coif. t. 4./. C. (bad), i
In ditches, not rare. Filaments dark-green, intensely lubricous, as thick
as horse-hair, rigid, forming large masses. Articulations usually a little*
longer than broad ; but Capt. Carmichael has found them six times as
long as their diameter. After conjugation, the filaments become crisped,
fragile, and lose much of their lubricity; the spires are soon after deranged
and the contents of one articulation discharged through its tube
into the opposite one, where they form a dark-coloured globule. The
other species undergo similar changes.
2. Z. deciminum, Ag. (two-spired Zygnema); filaments darkgreen
parallelly joined, spires double cruciate. Ag. Syst. Alg.
p. 81.— Conferva jvgalis, Dillw. Conf t. 5, and C. nitida, t. 4.
/. A. B.
Ditches, extremely common.—Very variable in the length of the
joints. Spires double, crossing each other, like a continual multiplication
of the Roman numeral X, whence the specific name.
3. Z. quininum, Ag. (one-spired Zygnema); filaments pale
yellow-green parallelly joined, spires simple. Ag. Syst. Alg.
the same author.—
p. 80 ; also Z. longatum and condensation of
Conferva spiralis, Dillw. Conf. t. 3, and C. longata, Syn.
Coif. p. 49.
Ditches and ponds, very common, forming cloudy pale-green masses.
—Filaments marked with a spiral line, resembling a multiplication of the
numeral V.
4. Z. cur vdtum, Ag. (curved Zygnema); filaments green unbranched
very slender here and there slightly bent and combined
by their angles, joints cylindrical four times as long as
broad, colouring matter in a triple irregular series of dots. Sm.
—Ag. Syst. Alg. p. 79 Conferva stictica, E. Bot. t. 2463.
Ditches in Henfield level, Sussex, Mr. Borrer.—This species appears
to be intermediate between the Genera Mougeotia and Zygnema.
" When young, the colour is a dull pale-green, and about 3 imperfectly
spiral lines of shining granules are with difficulty distinguishable :
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after-
wards these lines become more conspicuous, the rest of the filaments
being now perfectly colourless, and their component granules larger, but
their arrangement is still irregular. The threads subsequently unite here
and there, not by every joint, and their connecting processes are usually
nearer to one end of the joint than to the other. Such filaments are
divaricated at the points of connection, rather less abruptly than in Z
genufiexa. In some of the combined joints the contents appear un-