ZYGNEMACEJS. 89 



Zygnema neglectum, Hass. Alg. t. 23, f. 1 (not Petit). Hass. 

 Ann. Nat. Hist. x. 37. Jenner Fl. Tunb. Wells 178. 



In ponds. Fruiting in August. 



This species is rather a characteristic one, of which it appears to us 

 that Zygnema neglectum, Hass., is only a form with three chlorophyll 

 bands. If the two species of Hassall are drawn to the same scale, it is * 

 difficult to indicate any specific difference. The Rhynchonema rostratum 

 of Kntziiig is referred by Cleve to this species, but the Zygnema 

 rostratum of Hassall appears to be different, with thicker filaments and 

 much longer zygospores, and is rather referable to Spvrogyra nitida. 

 The Spirogyra neglecta of Petit cannot be the Zygnema neglectum of 

 Hassall. 



This species is thus described by Hassall : " Filaments about a foot 

 in length, with truncate extremities ; of considerable though rather less 

 diameter than those of S. nitida, mucous, glossy, and of a deep and 

 beautiful green colour ; investing membrane of the cells very evident 

 and transparent. Cells in the young filaments scarcely so long as broad, 

 but their length exceeds their breadth in those which have conjugated ; 

 round the interior of the cells five or six loose spiral tubes may be 

 faintly discerned ; these contain the reproductive globules (sic;), which 

 are large and distinct, with a dark central nucleus. Sporangia oval 

 sometimes almost circular and flattened, lying in inflated cells, the 

 cavity of which they do not fill." 



Plate XXXIV. fig. 2. a, sterile cells X 200; b, conjugating cells with 

 zygospores X 200 ; c, fertile cells of Rhynchonema form with zygospore 

 X 200 ; d, outline of zygospore X 400. 



B. Chlorophyll bands single or double (rarely ternate). 

 Spixogyra porticalis. Vauch. 



Sterile cells with the extremities truncate, 2 to 4 times 

 longer than the diameter ; chlorophyll bands single, or binate, 

 rarely ternate. 



Spores obtuse, ovoid, 1^ times longer than the diameter, 

 membrane even, chestnut colour. 



Sporiferous cells equal to the length of the spore, or twice as 

 long, more or less turgid. 



SIZE. Cells -032--05 mm. diam. Zygospore -08 X O48--05 

 mm. 



Cleve Monog. Zygn. p. 22, t. 5, f. 8 to 13. 



Conjugata porticalis, Vauch. Conf. p. 66, t. 5, f. 1. 



In ditches, &c. Fruiting in spring. 



a. quiniiia. 



Chlorophyll bands usually single. 



SIZE. Cells -035--045 mm., about twice as long. 



Zygnema quinmum, Hass. Alg. t. 28, f. 1, 2. Harv. Man. p. 

 143. Landsborough Brit. Seaweeds p. 362. Eng. Fl. v. 362. 

 Eng. Bot. Ed. ii. p. 175. Harv. Man. 143. Johnst. Fl. Berw. 

 ii. 256. Grev. Fl. Ed. 320. Mac. Fl. Hib. 231. Fl. Devon 

 ii. 50. Hook. Fl. Scot. ii. 80. Dickie Bot. Guide, 296. 



