SPIROT^NIA. 47 



Geogr. Distribution. Silesia in Germany. Austria. 



This is a rare plant and is readily distinguished by the 

 sharp apices of the cells. The chloroplast usually contains 

 one pyrenoid and extends to the extreme points of the cells. 

 The spiral ridges are generally three or four in number,, rather 

 irregular, and they frequently join together. Lutkemiiller 

 gives 18 fjL as the length of his smallest specimen (only 2 4 

 times longer than broad), but we have seen no British 

 specimens so short as that. 



14. Spirotaenia tenerrima Arch. 



Spirotxnia tenerrima Arch, in Quart. Journ. Micr. Sci. 1870, p. 203 ; 



Cooke, Brit. Desna. 1886, p. 52 ; Liitkem. Gatt. Spirotsen. 1895, p. 54 ; 



Nordst. Index Desmid. 1896, p. 251; West & G. S. West, Alga-fl. 



Yorks. 1900, p. 41. 

 ? Spirotxnia gracillima Arch, in Quart. Journ. Micr. Sci. 1875, p. 116, t. 6 ; 



Nordst. Index Desmid. 1896, p. 133. 



Cells minute, very slender, 20 times longer than 

 their diameter, somewhat curved or arched and slightly 

 attenuated towards the poles, apices truncate (?) ; 

 chloroplast ....?, forming a single spiral. 



Length 31-42^; breadth 2'5-3'5/j. 



? [ENGLAND. Pilmoor, N. Yorkshire ! (PI. Ill, figs. 



16, 17.)] 



IRELAND. Dublin (Archer) . 



It is extremely doubtful whether the specimens from York- 

 shire really belonged to this species, or to the Desmidiaceae 

 at all ! The nature of the chloroplast was very obscure and 

 the specimens may have been forms of Rhaphidium fascicula- 

 tum var. aciculare. It is also doubtful whether the forms 

 described by Archer as two species are identical. Foi- 

 ls', tenerrima he says : "Exceedingly slender, being, however, 

 long as compared with the diameter ; the cells somewhat 

 curved or arched, slightly tapering, ends truncate, the endo- 

 clirome forming a single spiral reaching from end to end of 

 the cavity, self-division transverse ; " and for S. (jracilliina 

 he says : " Very minute, linear, extremely slender, very 

 slightly tapering, apices blunt, spiral turns very numerous; 

 a remarkable form from its extreme slenderness. Breadth 

 2'5-2'8 |U, about twenty times longer than broad." It may 

 be that these plants are distinct species, but Archer's descrip- 

 tions are insufficient. 



