8&0 ZYGOPHYCES. 
Zygnema stellinum. (Vauch.) Kutz. Tab. V.t.17, f. 2. 
Sterile cells 14 to 3 times longer than broad. 
Zygospore broadly ovoid, formed in one or other of the con- 
joined cells. Membrane brown, scrobiculate. 
Sporiferous cells commonly longer than the zygospore. 
Size. Cells -022 mm. Zygospore :04 x 03 mm. 
De Bary Conj. p. 78. Cleve Mon. Zyg. p. 28, t. 8, f. 9-11. 
Rabh. Alg. Eur. ii, 249. 
Conjugata stellina, Vauch. Conf. p. 75, t.7, f. 1. 
Thwaitesia Duriei, Mont. Fl. Alg. t. 15, f. 1. 
Tyndaridea stellina, Jenner Fl. Tunb. Wells. p. 182. 
In pools and ditches. 
Kirschner 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 Vaucherit 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 Zygnemacee. 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; 6, conjugat- 
ing threads and zygospores X 400. 
Zygnema Vaucherii. Ag. Syst. Aly. p. 77. 
Sterile cells 24 or 3 to 5 times as long as broad. 
Zygospores subglobose or broadly elliptic, produced in one 
or other of the conjugating cells, which is usually more or less 
inflated, sporoderm delicately punctate. 
Sizz. Cells :01-022 mm. Zygospore, according to the 
varieties. 
Rabh. Alg. Eur. iii. 250. 
Conjugata gracilis, Vauch. Conf. t. 6, f. 2. 
Tyndaridea bicornis, Hass. Alg. 162, t. 38, f. 5. 
Tyndaridea interposita, Hass. Ann. Nat. Hist. x. p. 43. 
In ditches, ponds, &c. 
var.a. tenue. Rabh. Alg. Eur. 111. p. 250. 
Sterile cells -019--022 mm., 1 to 3 times as long. 
var. b. subtile. Rabh. Alg. Eur. ut. p. 250. 
Sterile cells 015-019 mm., 2 to 4 times as long. 
Tyndaridea ovalis, Hass. Alg. t. 38, f. 8. 
