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7 8 ZYGOPHYOBÆ.
malum, which, however, is not the Tyndaridea anómala of Ralfs and
Hassall, as will be evident hereafter. There does not seem to be even
a sufficient difference to justify the maintenance of the different forms
as varieties. This is the only British species, as far as at present known,
with a scrobiculate zygospore, produced in the channel of conjugation.
We have followed De Bary in referring this species to Zygnema instead
of to Zygogonium. I t is unnecessary in a work of this kind to discuss
the reasons which have induced ns in this, and similar cases, to adopt
such a course. I t may be well to caution the student at once_ that he
will only waste time in the endeavour to determine species from the
sterile threads. In the present, for instance, he would soon discover
how hopeless it is to attempt to discriminate between the vegetative
cells of this and some of its allies, without the knowledge also of the
method in which the zygospore is formed, and its character when developed.
Flate X X IX . fig. 1. a, portion of sterile thread X 400 ; b, threads
in conjugation X 200; c, zygospore X 400.
Zygnema R a lfs ii. (Kutz.) De Bary Conj. p. 77.
Sterile cells 2^ to 3 (rarely 4) times a,s long as broad.
Zygospore compressed ellipsoid, twice as long as broad,
produced in tbe inflated conjunctive canal. Sporoderm even.
S iz e . Cells -O ie -'O n X ■02mm. Zygospore '025 X -015 mm.
Eabb. Alg. Eur. iii. p. 252.
Zygogonium Ralfsii, Kutz. Tab. v. t. 11, f. 2. Kirsob. Alg.
Scbi. p. 127.
Tyndaridea Ralfsii, Hassall Alg. p. 165, t. 39, fig. 4, 5.
Ann. Nat. Hist. xii. p. 188, t. 7, f. 20. Jenner El. Tunb.
Wells, p. 182.
In pools and streams.
This is the only other British species of Zygnema which the zygospore
is produced in the channel, except the succeeding one, which is at
best doubtful. I t appears to be uncommon, at least in conjugation.
First fonnd by Mr. Balfs at Penzance. I t is still to be obtained in its
old habitat, and it appears to have been discovered in France and Germany.
. .
From the brief note of De Bary, he seems to recognise this as a distinct
and veritable species of Zygnema, according to his interpretation of
th a t geniis.
Rlate X X IX . f g . 2. a, portion of sterile thread X 400; b, threads
in conjugation X 400.
Zygnem a p a rvu lum . (Kutz.)
ste rile cells 4 to 6 times as long as broad, zygospore globose,
produced In tbe conjunctive canal.
S iz e . Cells ■02--022 mm. Zygospore about equal.
Zygogonium parvulum, Kutz. Tab. v. t. 12, f. 4. Kutz. Sp.
Alg. p. 447.
Zygnema ordinarium. Berk. Glean. 1 .12, f. 1. Harv. Man. 144.
In standing pools.
If the Zygnema ordinarium of Berkeley’s “ Gleanings ” can be referred
to Zygnema parvulum, that is, as far as we have ascertained,
the whole evidence upon which this species is inserted. The figure iu
the “ Gleanings,’’ as represented, in part, on onr plate 29 (fig. 3o), is so
manifestly insufficient, without measurements, that the species is introduced
with some hesitation. The rest of our figures, and the description,
are derived from Continental sources, and represent Kutzing’s
species.
Berkeley says of the plant he has fignred :—“ The filaments are
quite unattached, and float in a rather dull green mass at the top of the
water, which (at least in a state of fructification) is but little mucous,
adhering imperfectly to paper in drying. But as the plant has only been
once met with, and it is well known that other species of Zygnema are
much less mncous in a state of fructification, it is uuoertain whether
this is peculiar at all to the species. Articulations 4 to 6 times as long
as broad, at first filled with a yellowish green sporaceous mass, without
any marked pellucid border, with a single row in the centre of from 5 to
7 larger granules. The mass at length contracts, and the row of granules
is no longer visible. Short tubes are thrown out from the centre of the
joints, by which the filaments are at length connected into a more or less
intricate mass, and in the tubes a globular seed is formed, which swells
them, and is furnished with a pellncid border. In general the spora-
oeous matter of only one articulation passes into the tube to form the
seed ; nor in such case does the joint, of which the contents still appear
unaltered, throw out another tube. Fonnd at Glapthorn, Northamptonshire,
iu the spring of 1826, in watery spots of an exposed, ill-drained
field.”
Plate X X IX . fig. 3- a, portion of sterile thread X 400 ; b,
threads in conjugation X 200 ; e, conjugating cells and zygospores of
Zygnema ordinarium, after Berkeley, magnification unknown.
B . Zygospores produced in one or other o f the conjugating cells.
Zygnema c iu c ia tum . (Vauch.)
Sterile cells equal or twice as long as broad.
Zygospore spbærical, formed in one or other of two conjoined
cells. Membrane brown and scrobiculate.
Siz e . Cells ’028 mm. broad. Zygospore ’04 mm. diam.
Oleve Mon. Zygn. p. 29, t. 9, f. 1-3. Kirsob. Alg. Scbl. p.
126. Kutz. Tab. Pby. v. t. 17, f. 4.
Conjugata cruciata, Vauch. Hist. Conf. p. 76, t. 7, f. 2.
Tyndaridea cruciata, Hass. Alg. 160, t. 38, f. 1. Eng. Bot.
Ed. 2, t. 2512 B. Eng. El. v. p. 361. Mack, Hib. 231.
Conferva bipunciata, Dillw. Conf. t. 2. Hook El. Scot. ii, 81.
Zygnema bipunctatum, Jo b n st. El. Berw. ii, 256. Gray Arr.
i, 296.
Zygnema Dillwyni, Kutz, Tab. Pby. v. t. 17, f.
In ditches, pools, &c.
The form figured by Dillwyn is more slender than the typical form
and is considered by some as a distinot variety.
There is, perhaps, some difficnlty in determining the exact limits of
the three species L. cruciatum, L. stellinum, a n d i . Yaucherii, unless by
merging the latter two in one, and accepting Z. cruciatum as possessing
globose zygospores, whilst the other species has oval, or somewhat elou-
gated zygospores.
Plate XXX. fg. I. a, portion of sterile thread X 400; h, conjugating
threads with zygospores X 200 ; e, mature zygospore X 400.
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