88 ZYGOPHYCEE. 
Size. Cells ‘11-14 mm. diam.; zygospores ‘1 mm. diam. 
Narrow diameter -08 mm. 
Petit Spirogyra p. 31, t. 12, f.1, 2. Kutz. Tab. v. t. 27, f. 
8. Kirsch. Alg. Schl. p.118. Rabh. Alg. Eur. iti. 245. 
Zygnema orbiculare, Hass. Alg. p. 138, t. 19. Jenner FI. 
Tunb. Wells 178. 
Zygnema alternatum, Hass. Alg. 139, t. 20. 
Zygnema interruptum, Hass. Alg. 140, t. 21. Ann. Nat. 
Hist. 1843, p. 432. 
Zygnema maximum, Hass. Ann. Nat. Hist. x. (1842), p. 36 
Spirogyra alternata, Kutz. Spec. 442. Rabh. Alg. iii. 248. 
Spirogyra setiformis, Kutz. Tab. v. t. 28, fig. 1 (not Petit). 
Rabh. Alg. iii. 246. Cleve Mon. Zyg. p. 15 (in part). 
In ponds, &c. Fruiting in autumn. 
There is nothing inconsistent in Cleve’s suggestion that Hassall’s 
three plates 19, 20, and 21 all belong to the same species. No reliance 
can be placed on the width of the chlorophyll bands, nor the little 
difference in the breadth of the cells. Of course the disturbance in the 
bands of the conjugated cells is due to the conjugation. When this 
species is really in fruit there can be no difficulty in its determination, 
and, without fruit, it is folly to waste time in attempting to guess at the 
relationship of any species. 
Hassall says that “it is found in ponds and dykes whose waters are 
deep and permanent, and it does not conjugate until near the end of 
summer.” “Cells when in a state of conjugation, a little longer than 
broad, prior to which, however, they are frequently not half so long as 
broad; winding round the interior of these are about eight spiral 
threads, the granules in them being small.” 
Plate XXXIV. fig.1. a, sterile cells X 200; 6, conjugating cells with 
zygospores X 200; ¢, outline of zygospore X 400. 
Spirogyra bellis. Hassall. 
Sterile cells with the ends truncate, and usually 14 times 
(rarely 8 times) as long as broad; chlorophyll bands 5 to 6, 
making 3 to 1 turn, or nearly erect. 
Spores orbicular, depressed, with the membrane punctate or 
porose, chestnut colour. 
Sporiferous cells persistent, swollen. 
Germinating plant cylindrical, radical cell short and sub- 
cylindrical. 
Sizz. Cells 07-08 mm.; zygospore °07--08 mm. diam., 
*05--06 mm. thick.- 
Cleve Monogr. Zygn. p. 18, t. 8, f. 2to 5. Petit Spir. p. 
31, t. 10,f. 1 to 3. 
Zygnema bella, Hass. Alg. p. 142, t. 24. Ann. Nat. Hist. 
x. (1842), p. 37. Jenner Fl. Tunb. Wells 178. 
Spirogyra subequa, Kutz. Tab. Phy. v. t. 26, f. 2. 
Rhynchonema rostratum, Kutz. Tab. Phy. v.t. 34, f. 3. (Not 
Zygnema rostratum, Hass. Alg. t. 33, f. 1.) 
