44 lilUTISH DESMIDIACK.K. 



ENGLAND. Bowness, Westmoreland (Bissctt). En- 

 bridge Lake, Hants (Roy). Cornwall (Marquand). 



'WALES. Glyder Fact, Carnarvonshire (at 2,200 ft.) ! 



SCOTLAND. Nairn, Aberdeen, Kincardine, Forfar, 

 Perth (Roy fy Biw-tt). Rhiconich, Sutherland ! 



IRELAND. Dublin and Wicklow (ArrJtrr). 



Distribution. Austria. Sweden. Brazil. 



This species is sufficiently distinct by reason of the form of 

 tin 1 cells and the narrow chloroplast with few turns. We are 

 indebted to Dr. J. Liitkemiiller for accurate figures of this 

 plant. 



Section 2. Polyta&nise Rabenh. 



Chloroplast axile, cristate, with several spirally 

 arranged ridges revolving to the left, rarely almost 

 straight ; with one axile series of pyrenoids. 



10. Spirotaenia obscura Ralfs. 

 (PI. Ill, figs. 7-12.) 



Spirotxnia obscura Ralfs, Brit. Desm. 1848, p. 179, t. 34, f. 2 ; DC Bary. 

 Conj. 185S, p. 75 ; Arch, in Pritch. Infus. 1861, p. 752 ; Eabunh. F\<n\ 

 Europ. Alg. Ill, 1868, p. 147; Wolle, Desm. U.S. 1884, p. 33, t. 3, 

 L 16-19; Cooke, Brit. Desm. 1886, p. 52, t. 19, f. 6; Liitkem. <i;ilt. 

 Spirotsen. 1895, p. 2, 93, t. 1, f. 1-6, 15-19 ; Nordst. Index Desmid. 

 1896, p. 186 ; Koy. & Biss. Scott. Desm. 1894, p. 58 (sep.) ; West & 

 G. S. West, Alg. S. England, 1897, p. 478. 



Cells of medium size, 3-|-8 times longer than their 

 diameter, cylindrical or fusiform, attenuated towards 

 each pole, apices rounded ; chloroplast axile, not quite 

 reaching the poles, cristate, with 3-8 ridges spirally 

 twisted to the left, rarely almost straight, ridges 

 thickened at the free margin; pyrenoids several. 



Zygospore globose, areolate. 



Length 50-210 A*; breadth 15-30,,. 



ENGLAND. -- Westmoreland (Biwtt). JN T . Yorks ! 

 Lancashire ! Warwick (Will*). Kent (Ru-lfx). Sur- 

 rey ! Hants (Rot/). Cornwall (Ralfs). 



WALES. -- Capel Curig ! (GooJce ty Wills); Llyn 

 Idwal ! ; Y Foel Fras, Carnarvonshire ! 



