ZYGNEMACEE, 79 
the whole evidence upon which this species is inserted. The figure in 
the “ Gleanings,” as represented, in part, on our plate 29 (fig. 3c), is so 
manifestly insufficient, without measurements, that the species is intro- 
duced with some hesitation. The rest of our figures, and the descrip- 
tion, are derived from Continental sources, and represent Kutzing’s 
species, 
Berkeley says of the plant he has figured :—‘‘The filaments are 
quite unattached, and float in arather 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 mucous in a state of fructification, it is uncertain 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 pellucid border. In general the spora- 
ceous 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. Found at Glapthorn, Northampton- 
shire, in the spring of 1826, in watery spots of an exposed, ill-drained 
1d.” 
Plate XXIX. fig. 3. a, portion of sterile thread X 400; 2, 
threads in conjugation X 200; c, conjugating cells and zygospores of 
Zygnema ordinarium, after Berkeley, magnification unknown. 
B. Zygospores produced in one or other of the conjugating cells, 
Zygnema cruciatum, (Vauch.) 
Sterile cells equal or twice as long as broad. 
Zygospore spherical, formed in one or other of two conjoined 
cells. Membrane brown and scrobiculate. 
Size. Cells 028 mm. broad. Zygospore :04 mm. diam. 
Cleve Mon. Zygn. p. 29, t. 9, f. 1-3. Kirsch. Alg. Schl. p. 
126. Kutz. Tab. Phy. 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. Fl.v.p.361. Mack. Hib. 231. 
Conferva bipunctata, Dillw.Conf. t.2. Hook Fl. Scot. ii, 81. 
Zygnema bipunctatum, Johnst. Fl. Berw. ii, 256. Gray Arr, 
i, 296. 
Zygnema Dillwyni, Kutz. Tab. Phy. 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 distinct variety. 
There is, perhaps, some difficulty in determining the exact limits of 
the three species L. cruciatum, L. stellinum, and L. Vaucherti, unless by 
merging the latter two in one, and accepting Z. cruciatum as possessing 
globose zygospores, whilst the other species has oval, or somewhat elon- 
gated zygospores. 
Plate XXX. fig.1. a, portion of sterile thread X 400; 6, conjugat- 
ing threads with zygospores X 200 ; c, mature zygospore X 400, 
