88 ZYGOPHYCE.E. 



SIZE. Cells '11--14 mrn. diam. ; zygospores '1 mm. diam. 

 Narrow diameter '08 mm. 



Petit Spirogyra p. 31, t. 12, f. 1, 2. Kutz. Tab. v. t. 27, f. 

 3. Kirsch. Alg. Schl. p. 118. Rabh. Alg. Eur. iii. 245. 



Zygnema orbiculare, Hass. Alg. p. 138, t. 19. Jenner Fl. 

 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 setifonnis, 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. , sterile cells X 200 ; b, conjugating cells with 

 zygospores X 200 ; c, outline of zygospore X 400. 



Spirogyra bellis. Hassall. 



Sterile cells with the ends truncate, and usually 1^ times 

 (rarely 3 times) as long as broad ; chlorophyll bands 5 to 6, 

 making -^ 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. 



SIZE. Cells 07-'08 mm. ; zygospore *07-'OS mm. diam., 

 05-'06 mm. thick. 



Cleve Monoor. Zygn. p. 18, t. 3, f. 2 to 5. Petit Spir. p. 

 31, t. 10, f. 1 to 3. 



Zyqnema beUa, Hass. Alg. p. 142, t. 24. Ann. Nat. Hist, 

 x. (1842), p. 37. Jenner Fl. Tunb. Wells 178. 



Spirogyra subcequa, Kutz. Tab. Phy. v. t. 26, f. 2. 



Rhynchonema ro stratum, Kutz. Tab. Phy. v. t. 34, f. 3. (Not 

 Zygnema rostratwn, Hass. Alg. t. 33, f. 1.) 



