168 BRITISH DESMIDIACE^E. 



p. 289; Alg. W. Ireland, 1892, p. 155; Eoy & Biss. Scott. Desm. 189-4, 

 p. 170; Nordst. Index Desm. 1896, p. 191; West & G. S. West, Alg. 

 S. England, 1897, p. 490 ; Schmidle, Lappmark Siisswasseralgen, 1898, 

 p. 32 G. S. West, Variation Desm. 1899, p. 391, t. 11. f. 1-4; West & 

 Of. S. West, Alga-fl. Yorks. 1900, p. 72 ; Alg. N. Ireland, 1902, p. 42 ; 

 Notes Algae, III, 1903, p. 75. 

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



Cells rather small, a little longer than broad, deeply 

 constricted, sinus narrow with a slightly dilated 

 extremity ; semicells subelliptic or subreniform-elliptic, 

 dorsal margin somewhat more convex than ventral 

 margin, median part of apex rarely straight. Side 

 view of semicell circular. Vertical view elliptic, ratio 

 of axes about 1 : 1'3. Cell- wall granulate; granules 

 relatively large, and somewhat distant, normally 

 arranged in 7 or 8 vertical series, with 3 or 4 granules 

 in each series (median granules rarely duplicated), 

 11 to 14 visible at the margin of the semicell; in the 

 vertical view the granules are sometimes approximately 

 arranged in transverse series, and at other times there 

 is a clear central space. Chloroplasts axile, one in 

 each semicell, with a central pyrenoid. 



Zygospore unknown. 



Length 32-36 ju ; breadth 28-33 /* ; breadth of isth- 

 mus 9-5-11 iu; thickness 18-24 /<. 



ENGLAND.- -Cullingworth, W. Yorks! Thursley 



Common, Surrey ! JSTew Forest, Hants ! 



tj 



WALES. Capel Curig and Llyn-y-cwn-ffynon, Car- 

 narvonshire ! 



SCOTLAND.- -Aberdeen, Kincardine, Forfar !, Perth, 

 Argyll (Roy fy Bisxett}. Sutherland! Lewis and 

 Harris, Outer Hebrides ! 



ICELAND. Near Lough Machugh, Donegal ! Derry- 

 clare Louo-h and Ballynahinch, G-alway ! Grleno-ariff, 



IT" I 



JbLerry 



Geogr. Distribution.- -Austria and Galicia. Norway. 

 Sweden. United States. 



C. orthostichum is an uncommon species, apparently 

 restricted to the old deep Sphagnum-loogs and adjacent 

 boggy pools which are fed by bottom springs. It is 

 characterized by the possession of comparatively large 



