ZYGNEMACE^E. 91 



C. Chlorophyll bands single. 

 Spirogyra condensata. Vauch. 



Sterile cells with the extremities truncate, and commonly 

 1 to 3^ longer than the diameter. Chlorophyll bands single, 

 rarely two, making 1^- to 2 turns of the spiral. 



Spores broadly obtuse, ovoid, or subspherical, membrane even, 

 chestnut colour. 



Sporiferous cells turgid, and usually shorter than the spores. 



SIZE. Cells '04 mm. diam., zygospores *035-*04 mm. diam. 



Cleve Monog. Zygn. p. 21, t. v. f. 1-7. 



Conjugata condensata, Vauch. Conf. t. 5, f. 2. Gray Arr. 

 i. 298. 



Zygnema rarians, Hass. Alg. t. 29, f. 3 and 4. Jenner 

 Fl. Tunb. Wells, 180. 



Zygnema Woodsii, Hass. Alg. t. 33, f. 2. Jenner Fl. Tunb. 

 Wells, 180. 



'Spirogyra torulosa, Kutz. Tab. v. t. 20, f. 2. 



Spirogyra nodosa, Kutz. Tab. v. t. 20, f. 3. 



Spirogyra arcta, Kutz. Tab. v. t. 21, f. 2. 



Spirogyra condensata, Kutz. Tab. v. t. 22, f. 3. Petit Spiro- 

 gyra, p. 22, t. 9, fig. 6-8. 



Rhynchonema Woodsii, Kutz. Tab. v. t. 34, f. 2 (not of Nord. 

 and Wittr. Exs., No. 79). 



Spirogyra Flechsigii, Rabh. Hedw. i. p. 4G. 



Zygnema quininum, var. Hass. Ann. Nat. Hist. x. (1842) 35. 



Spirogyra ulotrichoides, Kutz. Tab. v. t. 21,f. 3. 



Spirogyra varians, Kutz. Sp. Alg. p. 439. Petit Spirogyra 

 p. 49, t. 4, f. 1-8. 



Spirogyra injiata, Kutz. Tab. v. t. 21, f. 1-8. 



In pools. Fruiting in spring. 



From the number of synonyms quoted above, it may be inferred that 

 this is a variable species. All the forms seem to be included by Petit 

 under his Spirogyra condensata and S. varians. 



Hassall thus alludes to a peculiar nodoluse growth of some of the 

 forms : " When a number of cells unite in regular order with those of a 

 neighbouring filament, no inflation of any of these occurs ; but it fre- 

 quently happens that several adjoining cells of a filament for some reason 

 or other do not unite, although the remaining ones in that filament do, 

 in which case those which have not yoked themselves swell up, assuming 

 a monoliform appearance, and at the same time frequently emit blind and 

 irregular processes or prolongations, by which the cells manifest the 

 strong tendency which they have to conjoin themselves, but which some 

 cause, not evident, would appear to have frustrated. In some speci- 

 mens the number of inflated cells and blind processes is but smali, 

 while in others the elongated cells are more numerous than those which 

 have united in the ordinary manner." A similar circumstance may 

 sometimes be observed in S. longata, especially in the short-celled 

 forms. 



O 



