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Zygnema s te llin um . (Vauchi) Kntz. Tab. V. t. Ÿ!, f . 2.
Sterile cells 1-| to 3 times longer than broad.
Zygospore broadly ovoid, formed in one or other of tbe conjoined
cells. Membrane brown, scrobiculate.
S poriferous cells commonly longer than the zygospore.
S i z e . Cells -022 m m . Zygospore -04 x ’08 m m .
De Bary Conj. p. 78. Cleve Mon. Zyg. p. 28, t. 8, f. 9-11.
Eabb. Alg. Eur. iii, 249.
Conjugata stellina, Vauob. Conf. p. 75, t. 7, f. 1.
Thwaitesia Duricei, Mont. El. Alg. t. 15, f. 1.
Tyndaridea stellina, Jenner FI. Tunb. Wells, p. 182.
In pools and ditches.
Kirechner unites this species and the next, for which he appears to
have great justification. We scarcely see how they can be maintained
as distinct if the broad view of Zygnema Vaueherii which we have
adopted is tenable.
No definite period can be fixed for the production of the zygospores,
not only in this species, but in the majority of the Zygnemaceæ. We
have observed them in June, or earlier, some as soon as April, and as
late as September. Hassall says “ the species may be found in a state
of conjugation during the entire of the spring, summer, and autumnal
months ; they are chiefly met with, however, in this state in the
spring.” Cleve has attached dates to the species enumerated by him,
but as these do not correspond with the periods at which we have found
them in this country, these dates are not quoted lest they should prove
misleading rather than useful.
Plate XXX. fig. 2. a, portion of sterile thread X 400 j b, conjugating
threads and zygospores X 400.
Zygnema V a u ch e iii. Ag. Syst. Alg. p . 77.
Sterile cells 2-|- or 3 to 5 times as long as broad.
Zygospores subglobose or broadly elliptic, produced in one
or otber of tbe conjugating cells, wbicb is usually more or less
inflated, sporoderm delicately punctate.
Size. Cells ■01--022 mm. Zygospore, according to tbe
varieties.
Eabb. Alg. Eur. iii. 250.
Conjugata gracilis, Vaucb. Conf. t. 6, f. 2.
Tyndaridea bicornis, Hass. Alg. 162, t. 88, f. 5.
Tyndaridea interposita, Hass. Ann. Nat. Hist. x. p. 43.
In ditcbes, ponds, &c.
var. a. te n u e . Rabh. Alg. E u r .m . p . 2t0.
Sterile cells -019-'022 mm., 1 to 3 times as long.
var. 6. su b tile . Rabh. Alg. Eur. m . p . 250.
Sterile cells -015--019 mm., 2 to 4 times as long.
Tyndaridea ovalis, Hass. Alg. t. 38, f. 8.
var. c. s ta g n a te . Kirsch.
Sterile cells -01 mm., 3 to 4 times as long.
Tyndaridea stagnalis, Hass. Alg. 162, t. 38, f. 9.
Tyndaridea stagnicola, Hass. Ann. N. Hist. x. (1842) p. 42.
Jenner FI. Tunb. Wells, p. 182.
I t will be seen frcm the abcve that this is a variable species, of which
twc of the three varieties are British. These are by no means nn.
common, often mixed with other filamentous algm, and can scarcely be
confounded with anything else, even when sterile.
Plate X X X . fig. 3. a, portion of sterile thread X 400; b, portion
of fertile thread with zygospores X 400. Fig. 4, var. subtile, a, portion
of sterile threads X 400; b, conjugating threads and zygospores X 400.
Fig. 5, var. stagnale. a, portions of sterile threads X 400 ; b, fertile
cells with zygospores X 400.
Z y g n em a a n om a lum . (Hass.)
Sterile cells equal, or nearly twice as long as broad ; cytioderm
thick, lamellose.
Zygospore globose, olivaceous (sporoderm distinctly punctate
?).
S iz e . Cells -025 mm. diam., with mucous sheatb about
double ; zygospore ‘026 mm. diam.
Tyndaridea lutescens, Hass. Alg. t. 38, f. 4. Dickie Bot.
Guide 296.
Tyndaridea cruciata, Harv. Man. p. 141.
Tyndaridea abbreviata, Hass. Ann. Nat. Hist. x. (1842) p. 43.
Tyndaridea anómala, Hass. Alg. t. 38, f. 2-3. Jenner El.
Tunb. Wells, 182. Ealfs, Eng. Bot. Supp. t. 2899.
In boggy pools.
The British species is the Tyndaridea anómala of Hassall and Ealfs,
and not the Zygnema anomalum of Continental botanists, which species
has the zygospore produced in the conjugating canal. The following is
the original description published by Ealfs in the supplement to “ English
Botany ” :—
“ I t forms large, dark green masses in shallow pools on heaths. The
filaments are sto u t; under the microscope each is found to be enclosed
in a hyaline sheath, which extends on each side about half the breadth
of the coloured portion, and is always more or less waved or scolloped.
At first ic is nearly even, but it gradually becomes more and more irregular,
and the conjugating specimens are almost denuded. The joints
of the filament are usually about equal in length and breadth, but
sometimes twice as long as broad. The endochrome is blackish green,
and at first quadrate, when it completely fills the joint, bnt its division
into two portions gradually becomes apparent until two stelte, bnt leas
distinct than those in the other species, are at last developed, when conjugation
takes place in the usual manner. The spores, which are
globular, are contained in the joints of one of the connected filaments.
Not unfreqnently the tubular processes are themselves converted into
cells containing endochrome.
“ In its early state this plant is so different in appearance from the
other species, that at first sight its proper situation is scarcely appa-
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