ZYGNEMACE^E. 97 



Zygnema varians, Hass. Ann. Nat. Hist. xi. (1843) p. 431. 

 Conjugata inflata, Vauch. Conf. p. 68, t. 5, f. 3. 

 Zygnema inflatum, Hass. Alg. t. 32, f. 6, 7. Jenner Fl. Tunb. 

 Wells, 180. 



Zygnema Jenneri, Hass. Alg. t. 37, f. 6. Jenner Fl. Tunb. 



Wells, 182. 



Zygnema dubium, Hass. Alg. t. 37, f. 7. 

 Spirogyra gastroides, Kutz. Tab. v. t. 29, f. 4. 

 Rliynchonema Jenneri, Kutz. Tab. v. t. 32, f. 1. 

 Rhynchonema dubium, Kutz. Tab. v. t. 32, f. 2. 

 Spirogyra inflata, Rabh. Alg. Eur. iii. 233. 



In pools. 



This species includes the most delicate of British species with repli- 

 cate ends to the cells. In all the forms of both varieties there is an 

 evident tendency in the fertile cells to become more or less inflated. The 

 only difference which Hassall indicates between his Z. inflatnm and Z. 

 tenuissimum is one of size, which may be influenced by the circum- 

 stances of growth. 



Plate XXXIX jig. 3. a, sterile cells X 200 ; b, conjugating cells of va- 

 riety a, with zygosporeaX 200; c, conjugating cells of variety b, with 

 zygospores X ^00 ; d, outline of zygospores X 400. 



GENUS 46. SIROGONIUM Kutz. (1843.) 



Cells with" parietal longitudinal chlorophyll bands. Fructi- 

 fying cells diverse, arising by unequal division of the thread- 

 cells, bending knee-like towards each other and growing 

 together, united at the point of adnation ; receiving-cells barrel- 

 shaped ; giving-cells short, cylindrical. Zygospore (elliptic) in 

 tbe receiving cell-wall. 



The sterile cells, with parallel chlorophyll bands, resemble those of 

 Spirogyra, but differ in the genuflexuous conjugation. 



Sirogonium sticticum. Kutz. 



Sterile cells 2 to 5 times as long as broad. 



Zygospore broadly elliptical, spore-coat double. 



Sporiferous cells swollen, abbreviated. 



SIZE. Cells -04 to '05 mm., 2 to 5 times as long. Zygospore 

 042 x '075 mm. 



De Bary Conj. p. 78, t. 2, figs. 1-6. Rabh. Alg. Eur. iii., 256. 



Sirogonium breviarticulatum, Kutz. Tab. Phy. v. t. 4. 



Sirogonium Braunii, Kutz. Tab. Phy. v. t. 4. 



Conferva stictica, Eng. Bot. t. 2463. 



Zygnema curvatum, Ag. Eng. Fl. v. 362. Harv. Man. p. 

 143. Eng. Bot. Ed. ii. t. 2512, f. A. Hassall Alg. 143, t. 26, 

 f. 1, 2. 



Choaspes serpentina, Gray Arr. 1, 299. 



In ponds and ditches and moor pools. 



