80 ZYGOPHYCEJE. 



Zygnema stellinum. (Vauch.} Kutz. Tab. V. t. 17, /. 2. 



Sterile cells 1^ to 3 times longer than broad. 



Zygospore broadly ovoid, formed in one or other of the con- 

 joined cells. Membrane brown, scrobiculate. 



S poriferous 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. Ear. iii, 249. 



Conjugata stellina, Vauch. Conf. p. 75, t. 7, f. 1. 



Thwaitesia Duricei, 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 Vaucherii 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 Zyynemacem. 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 ; b, conjugat- 

 ing threads and zygospores X 400. 



Zygnema Vaucherii. 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 other of the conjugating cells, which is usually more or less 

 inflated, sporoderm delicately punctate. 



SIZE. Cells '01-'022 mm. Zygospore, according to the 

 varieties. 



Rabh. Alg. Eur. iii. 250. 



Conjugata giacilis, 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. Ew. in. p. 250. 

 Sterile cells -019--022 mm., 1 to 3 times as long. 



var. b. subtile. Rabh. Alg. Eur. in. ^?. 250. 



Sterile cells -015--019 mm., 2 to 4 times as long. 

 Tyndaridea ovalis t Hass. Alg. t. 38, f. 8. 



