90 ZYGOPHYCE.E. 



Spirogyra quinina, Kutz. Tab. v. t. 22, f. 2. 



Spirogyra porticalis, Petit iSpirogyra, p. 21, t. 5, f. 8-12. 



Conferva spiralis, Dillw. Conf. t. 3. Eng. Bot. Ed. i. t. 1656. 



Zygnema spiralis, Eng. Bot. Ed. ii. t. 2561. 



Conjugata quinina, Gray Arr. i. 297. 



var. (3. decimina. 



Chlorophyll bands usually 2, sometimes 3. 



SIZE. Cells -034--04 mm., 2 to 4 times as long. 



Zygnema deciminum, Hass. Alg. t. 23, f. 3, 4. Harv. Man. 

 p. 143. Johnst. Fl. Berw. ii. 255. Mack. Fl. Hib. 2, 31. Fl. 

 Devon ii. 50. Jenner Fl. Tunb. Wells 178. Grev. Fl. Edin. 

 320. Eng. Fl. v. 362. 



Spirogyra decimina, Kutz. tab. v. t. 23, f. 3, 24, f. 1. Petit 

 Spirogyra p. 25, t. 8, f. 1-3. Rabh. Alg. iii. p. 242. 



Spirogyra flavicans, Kutz. tab. v. t. 23, f. 3. 



Spirogyra laxa, Kutz. Tab. v. t. 23, f. 3. 



Spirogyra major, Kutz. Tab. v. t. 24, f. 2. 



Conferva jugalis, Dillw. Conf. t. 5. 



Conferva inflata, Eng. Bot. Ed. i. t. 2376. 



Zygnema injlatum, Eng. Bot. Ed. ii. t. 2510. Hook. Fl. 

 Scot. ii. 80. 



Conjugata inflata, Gray Arr. i. 297. (?) 



Conjugata decimina, Gray Arr. i. 299. 



var. c. rivulaiis. Hass. 



SIZE. Cells "032--036 mm., 5 to 10 times as long. 

 Zygnema rivulare, Hass. Alg. 144, t. 27, f. 1, 2. Annals 

 Nat. Hist. x. 38. 



Spirogyra rivularis, Rabh. Alg. Eur. iii. 243. 



Undoubtedly if the nterile threads of this species are carefully ex- 

 amined, they will furnish abundant evidence that the number of spiral 

 bands is variable, for cells will constantly be found in the same filament 

 in which either one or two bands occur. So that, with the great simi- 

 larity in fruit, it would be folly to think of maintaining the two varieties 

 decimina and quinina as distinct species, on account of the number of 

 chlorophyll bands. The Z. rivulare of Has sail, which we have included 

 as a third variety, is not uncommonly found in a sterile condition, in so 

 far as it can be determined in this stage, but hitherto we have not seen 

 it in fruit. It is said to be found on the Continent in fructification, but 

 we have no knowledge of the Continental form. The spirals in the 

 sterile cells are usually three, and then very nearly identical with the 

 condition of the variety decimina, in which the bands are the same in 

 number, 



Plate XXXV. fig. ], form quinina. a, sterile cells X 200; b, c, conju- 

 gating cells with zygospores X 200 ; d, outline zygospores X 400. Fig. 2, 

 form decimina. a, sterile cells X 200 ; b, conjugating cells with zygo- 

 spores X 200 ; d, outline zygospore X 400. Fig. 3, form rivularis. a, 

 sterile cells X 200. 



