36 ERHTSH DESMIDIACE^E. 



minute granules, in tlie centre with 3-6 vertical coste, 

 sometimes smooth and indistinct, more rarely indis- 

 tinctly granulate. Side view of semicell rectangular, 

 basal angles slightly tumid, sides and apex faintly 

 retuse, apical angles minutely granulate. Vertical 

 view elliptic, with a broad 3-6-undulate inflation at 

 each side, poles subtruncate and minutely granulate. 

 Chloroplasts axile, with one pyrenoid in each cell. 



Zygospore globose, furnished with many stout ver- 

 rucas (about 16 visible at the margin), slightly at- 

 tenuated and 2-, 3- or 4-furcate at the apex. 



Length 27-43 (rarely to 59) p. ; breadth 22-31 

 (rarely to 44) p, ; breadth of isthmus 913 JJL ; thickness 

 14-22 (rarely to 28) JLL ; diam. zygosp. without verrucas 

 29 jn, with verrucas 38 JJL. 



ENGLAND. - -Cumberland ! Westmoreland ! Lanca- 

 shire (Ralfs). W. and N. Yorks ! Sub-fossil at Filey, 

 E. Yorks! Leicestershire (Roy). Gloucestershire 

 (Raffs). Surrey! Sussex, Hants, and Wilts ! (Ralfs). 

 Devonshire ! Cornwall ! 



WALES.- -Llyn Teyrn on Snowdon, Penmaenmawr, 

 Moelfre, near Dolbadarn Castle, Bethesda, Capel Curig 

 (Cooke fy Wills), Moel Siabod, and Llyn Cwlyd, Car- 

 narvonshire ! Merionethshire ! Glamorganshire ! 



SCOTLAND. - -Common ; zygospores from Muchalls, 

 Kincardine, and Rannoch, Perth (Roij $- Bissett). At 

 3500 ft. on Lochnagar ! Orkneys ! Shetlands ! Outer 

 Hebrides ! 



IRELAND. Donegal ! Galway ! Kerry ! Dublin and 

 Wicklow (Archer). Down (up to 2000 it.) ! 



Geoc/r. Distribution.- -France. Germany. Austria 

 and Galicia. Bosnia. Hungary. Roumania. Italy. 

 Norway. Sweden. Denmark. Bornholm. Finland. 

 N. and S. Russia. Faeroes. Iceland. Xova Zembla. 

 Spitzbergen. Greenland. Siberia. Japan. India. 

 Australia. Abyssinia. E. Africa. Azores. Sandwich 

 Islands. United States. Brazil. Ecuador. Argentine. 

 Patagonia. 



C. crenatum is largely an alpine and arctic Desniid. In 



