ZYGNEMACE. 83 
Zygnemainsigne. Kutz. Tab. v. t.17,f. 1. 
Sterile cells equal, or twice as long as broad. 
Copulation scalariform or lateral; zygospore globose or 
slightly oval; membrane brown, even. 
Size. Cells 026-03 mm. diam.; zygospore about ‘026 x 
‘032 mm., or globose about -03 mm. diam. 
De Bary Conj. p. 78, t. 8, £.14-16. Rabh. Alg. iii, 249. 
Kutz. Tab. v. t. 17, f.1. Kirsch. Alg. Schl. p. 125. 
Tyndaridea insignis, Hass, Alg. p. 163, t. 38, f. 6,7. Jenner 
Fl. Tunb. Wells 182. 
Zygnema tenue, Rabh. Exs. No. 674. 
In streams and ditches. 
The cells of this species at the time of conjugation are apt to become 
much distorted, inflated sometimes on one side, sometimes on the other, 
and even to conjugate in the manner represented by DeBary, and copied 
on our plate. : 
Plate XXXT. fig. 3. a, sterile cells X 400; 0, fertile cells with 
zygospores X 200; ¢, fertile cells, with longitudinal conjugation, X 200, 
after De Bary; d, zygospore X 400. 
Genus 45, SPIROGYRA. Link. (1820.) 
Cells with one to several parietal chlorophyll bands, usually 
spirally winding to the right. Copulation ladder-like (Spiro- 
gyra) or lateral (Rhynchonema). Zygospores always within the 
wall of one of the united cells. Copulating cells similar to the 
sterile ones, or swollen out. 
This genus, as now accepted, includes two genera as recognised by 
Kutzing, Spirogyra and Rhynchonema. In the former the conjugation 
was scalariform, and in the latter it was lateral. It is now found that 
in many species, probably in all, both kinds of conjugation take place, 
according to circumstances. The same filament, which in some portion 
of its length conjugates with a neighbouring filament, has also been 
observed conjugating laterally between two of itsown cells. The genus 
Rhynchonema therefore has thus been proved to represent only one of 
the modes of conjugation of the same plant, which under other condi- 
tions conjugates with a neighbouring filament. 
In past times too great importance was attached to the breadth and 
length of the cells in the sterile filaments, and also to the character of the 
spiral bands, features which are now known to be too variable to be relied 
upon, the most important and reliable characters being derived from the 
zygospore; hence only specimens in fructification can be accurately 
determined. 
The most recent work on the species of Western Europe is a Mono- 
graph of Spirogyra, as represented in France, by Mons. Paul Petit. 
(Paris, 1880.) See also Professor Cleve’s “‘ Monograph of the Zygnemacew.” 
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