176 BRITISH DESMIDIACE^;. 



167. Cosmarium sphalerostichum Nordst. 

 (PL LXXXI, figs. 12-14.) 



Cosmarium sphalerostichum Nordst. Desm. Ital. 1876, p. 29, t. 12, f . 3 ; 

 Cooke, Brit. Desm. 1887, p. Ill, t. 42, f. 6; Wolle, Freshw. Alg. U. S. 

 1887, p. 31, t. 57, f. 26-27; Boldt, Desm. G-ronland, 1888, p. 27 ; De Toni, 

 Syll. Alg. 1889, p. 1034 ; West, Alg. N. Wales, 1890, p. 290 ; Alg. W. 

 Ireland, 1892, p. 157 ; Alg. Engl. Lake Distr. 1892, p. 728 ; Roy & Biss. 

 Scott. Desin. 1894, p. 175 ; Nordst. Index Desm. 1896, p. 237 ; West 

 & G. S. West, Alg. S. England, 1897, p. 489; Alga-fl. Yorka. 1900, p. 72; 

 Alg. N. Ireland, 1902, p. 38 ; Freshw. Alg. Orkneys and Shetlands, 

 1905, p. 20 ; Borge, Beitrage Alg. Schweden, 1906, p. 32. 



Ursinella sphalerosticha Kuntze, Revis. gen. plant. 1891, p. 925. 



Cells very small, a little longer than broad, deeply 

 constricted, sinus narrow and linear ; semicells sub- 

 reniform-trapeziform with a much flattened base, 

 basal angles subrectangular, apex truncate and smooth, 

 lateral margins convex, furnished with 4 or 5 rather 

 acute granules; granules on the surface of the semicell 

 variable in number and disposition, but commonly in 

 transverse (2 or 3) and vertical (5 or 6) series, the 

 series being very frequently incomplete. Side view of 

 semicell circular. Vertical view elliptic, ratio of axes 

 about 1 : 1*3, margin granulate, granules at the poles 

 acute, those at the middle on each side rounded and 

 slightly larger, generally with one series of about 

 4 granules within each pole. Chloroplasts axile, each 

 with one pyrenoid. 



Zygospore globose or subglobose, black and smooth. 



Length 15*5-20 /m ; breadth 1 3-15'5 /u ; breadth of 

 isthmus 5-6 ,u ; thickness 10-12 /* ; diam. zygosp. 

 18-20 A <. 



ENGLAND. Cumberland ! Westmoreland ! Lanca- 

 shire ! W. and N. Yorks ! Surrey ! Wilts ! Devon ! 

 Cornwall ! 



WALES.- -Yr Orsedd, near Bethesda, Llyn Padarn, 

 Llyn Bochlwyd, Capel Curig, Llyn Cwlyd, Snowdon, 

 and Llyn Grwynant, Carnarvonshire ! Radnor ! 



SCOTLAND.- -Morven, Aberdeen ; Canlochan, Forfar 

 (Roy Bissett). Clova Mts., Forfar ! Ben Nevis, 

 Inverness ! Near Lerwick and near Scalloway, 

 Shetlands ! 



