96 ZYGOPHYCEE. 
Spirogyra inequalis, Kutz. Tab. v. t. 80, f. 3. 
Zygnema Grevilleanum, Hass. Alg. 149, t. 31, f.1,2. Hass, 
Ann, Nat. Hist. x. 38. Jenner Fl. Tunb. Wells, 180. 
form b. subventricosum. : 
Sporiferous cells 2 to 4 longer than the spores. Diam. 026 mm. 
Spirogyra Weberi, Rabh. Alg. Eur. iii. 233. 
Zygnema sub-ventricosum, Hass. Alg. 150, t. 32, f.4, 5. Jenner 
Fl. Tunb. Wells, 180. 
Zygnema diductum, Hass. Alg. t. 37, f. 4. 
Rhynchonema diductum, Kutz. Tab. v. t. 32, f. 3. 
Spirogyra ventricosa, Kutz. Tab. v. t. 29, f. 5. 
Zygnema ventricosum, Hass. Ann. Nat. Hist. x. (1842) p. 38. 
Zygnema longatum, Hass. Alg. 151, t. 31,f. 3, 4. 
In ditches. Fruiting in summer. 
The absence of any measurements, or uniformity in magnification in 
the figures, renders it very difficult to determine many of Hassall's 
species with any certainty. From present information we are unable to 
recognise Z. Grevilleanum as a distinct species. 
Plate XXXIX. fig. 2. a, sterile cells X 200; 5, c, conjugating cells 
with zygospores X 200; d, fertile cells of Rhynchonema form with 
zygospores X 200. 
Spirogyra tenuissima. Hass. 
Sterile cells with the extremities replicate, 5 to 15 times as 
long as the diameter. Chlorophyll bands single, making 3 to 6 
turns of the spiral. 
Spores broader than the sterile cells, elongated ovoid, twice 
as long as the diameter, membrane even and chestnut colour. 
Sporiferous cells turgid. 
Size. Spore -055 (a)--058 (8) x :024 (a)--03 mm. (8). 
Cleve Monog. Zygn. p. 24, t. 6, f. 5-7. 
jorm a, tenuissima. 
Sterile cells 8 to 16 times as long as broad. -012-015 mm. 
diam. 
Sporiferous cells 2 to 3 times as long as the spores. 
Zygnema tenuissimum, Hass. Alg. t. 82, f. 9,10. Ann. Nat. 
Hist. x. (1842) p. 41. Jenner Fl. Tonb. W., 180. 
Zygnema minimum, Hass. Alg. t. 37, f. 8. 
Spirogyra tenuissima, Kutz. Tab. v, t.29,f.2. Rabh. Alg. 
Eur. iii, 233. 
Rhynchonema minimum, Kutz. Tab. v. t. 33, f. 1. 
Spirogyra Naegelit, Kutz. Tab. v. t. 29, f. 3. 
form b. inflata. 
Sterile cells 5 to 10 times as long as broad. ‘017-02 mm. 
diam, 
Sporiferous cells scarcely longer than the spores. 
