256 BRITISH DESMIDIACE.E. 



f. 5 ; Brit. Desm. 1848. p. 58, t. 3 ; Arch, in Pritch. Infus. 1861, p. 723, 



t. 2, f. 38, 39. 



Bambusina Borreri Delp. Spec. Desm. subalp. 1877, p. 54, t. 2. f. 1-7. 

 Gymnozyga Brebissonii Wille in Engler. Natur. Pflanzenfam. 1890, p. 15, 

 't. 9 J ; Hustedt, Desm. Bac. Tirol, 1911, p. 342. 



Filaments twisting, formed of rather barrel-shaped 

 cells ; semicells with a small basal inflation, and an 

 extremely slight median constriction ; lateral margins 

 straight except for the broad rim at the base, apex 

 broad and truncate ; cell- wall often showing very 



o / 



delicate longitudinal striations ; vertical view circular, 

 sometimes with two opposite mamillse. Chloroplasts 

 axile, one in each semicell, each having a central pyrenoid 

 and about 6 radiating plates. 



Zygospores oval and smooth. 



Length 25-30 u. ; breadth 17'5-22'o \L ; length of 

 zygospore 25-30 pi ; breadth 16-20 pi. 



ENGLAND. Cumberland ! Westmoreland, and in the 

 plankton of Codale and Easedale Tarns ! Lancashire 

 (Balfs). W., N., and E. Yorks ! Warwicks (Wills). 

 Surrey ! Sussex (Rolfs). Hants ! Devon ! (Harris). 

 Cornwall ! 



WALES. General ! In the plankton ! 



SCOTLAND. General ! zygospores from Aberdeen, 

 Kincardine, Perth and Argyle (Roy & Biss.). Lewis and 



Harris, Outer Hebrides ! Hov, Orkneys ! Not un- 



7 \j ' / 



common in the plankton ! 



IRELAND. General ! Zygospores from near Recess, 

 Galway ! Mayo ! Plankton of Galway and Kerry ! 



Geogr. Distribution. France. Germany. Switzer- 

 land. Austria and Galicia. Bohemia. Hungary. Italy. 

 Spain. Norway. Sweden. Denmark. Finland. N. 

 Russia. Spitzbergen. Manchuria. India. Ceylon. 

 Burma. Singapore. Java. Australia. New Zealand. 

 E. Africa. Sandwich Isles. United States. Guiana. 

 Brazil. Colombia. 



Var. gracilescens Nordst. (PL CLXV, fig. 10 ; 



PL CLXVI, fig. 10.) 



Bambusina Borreri var. gracilescens Nordst. in Wittr. & Nordst. Alg. Exs. 

 fasc. 7, 1880, no. 367, fasc. 21, 1889, p. 34. 



