ZYGNEMACEJ2. 93 



Spirogyra turpis, Kutz. Tab. v. t. 19, f. 2. Rab. iii. 238. 

 Spirogyra catceneformis, Kutz. Tab. v. t. 19, f. 1. Rab. iii. 

 238. Petit Spirogyra t. 3, f. 9-12. 



Rhynchonema abbrevialum, Kutz. Rab. iii. 248. 



We venture to differ from onr friend Mons. Petit in uniting four of his 

 species. Iu fact, if four species are to be accepted, we see no logical 

 grounds for refusing to accept a dozen, because of the excessive vari- 

 ability in the sterile cells. 



Plate XXXVI. Jic/, 2. a, b, sterile cells X 200; c, conjugating cells 



with zygospores X 200; d, fertile cells of RJiynchonema form with zygo- 



spore X 200 ; e, fertile cells of mirabilis form with zygospores X 200 ; 



f, conjugating cells of catenceformis form with zygospores X 200 ; g t Ji, i t If, 



outline zygospores X 400. 



Spirogyra flavescens. (HassJ Cleve. 



Sterile cells with the ends truncate, 2 to 5 times longer than 

 broad, chlorophyll bands single. 



Spores attenuated, twice as long as broad, membrane even, 

 chestnut colour. 



Sporiferous cells swollen, and usually longer than the spores. 



SIZE. Cells '02 mm. diam. Zygospore -05 X '024 mm. 



Cleve Monog. Zygn. p. 19, t. 3, f. 6, 7. 



Boggy pools on heaths, &c. 



form a. gracilis. 



Zygospore about '03 mm. diam. 

 Zygnema gracile, Hass. Alg. t. 30, f. 5, 6. 

 Spirogyra gracilis, Kutz. Tab. v. t. 18, f. 5. Petit Spiro- 

 gyra p. 15, t. 3,f. 7, 8. 



Zygnema malleolum, Hass. Alg. t. 34, f. 5. 

 RJiynchonema malleolus, Kutz. Tab. v. t. 33, f. 3. 



form b. flavescens. 



Zygospore about '02 mm. diam. 



Zygnema Jlavescens, Hass. Alg. t. 30, f. 9, 10. Jenner Fl. 

 Tunb. Wells, 180. 



Spirogyra Jlavescens, Kutz. Tab. v. t. 18, f. 4. Petit Spiro- 

 gyra p. 15, t. 3, f. 5, 6. 



Zygnema affine, Hass. Alg. t. 34, f. 6. 



Spirogyra affinis, Petit fcpirogyra, p. 18, t. 3, f. 12, 13. 



RJiynchonema affine, Kutz. Tab. v. t. 33, f. 2. 



form c. parva. 



Zygospore about '01 mm. diam. 



Zygnema parvum, Hass. Alg. t. 30, f, 7, 8. Ann. Nat. Hist, 

 x. (1842) p. 41. Jenner Fl. Tunb, Wells, 180. 

 Spirogyra parva, Kutz. Tab. v. t. 18, f. 3. 



This species includes five of Hassall's species of Zygnema, which sub- 

 sequently were relegated by Ktitzing, three to Spirogyra and two to 

 Ehynchon&ma. The Zygnema Jlavescens, parvum, and gracile, are sepa- 



