204 BRITISH DESMIDIACI'LE. 



and considerably attenuated from the middle to the 

 apex, with a slight but distinct basal inflation ; apices 

 truncate or convexo-truncate, with a ring 1 of 13-15 

 small, depressed, apical tubercles (7-8 visible across 

 the apex) ; cell-wall punctate. 



Zygospore unknown. 



Length 380500 (very rarely up to 700) /u. ; breadth 

 in middle of semicells (maximum breadth) 04-75 /z ; 

 breadth at apices 29-40 ^. 



ENGLAND. Cumberland! Westmoreland ! (///**<//). 

 W. and N. Yorks! Leicester (//"//). Suffolk! Warwick! 

 (ir/7/.s). Surrey! (AW/*). Sussex (R<ilf*). Hants. 

 (Boil). Cornwall! (Balfo). 



WALKS. Capel Curig ! (Cooke fy IT/V/.s), Siiowdon (at 

 over 3,000 ft.) ! , and Llyn Padarn ! , Carnarvonshire. 



SCOTLAND. General ! (lunj fy Bisiwlt). Outer 

 Hebrides ! Shetlands ! 



IRELAND. Mayo ! Gal way ! Kerry ! Dublin and 

 Wicklow (Ai'cln'f). 



(ii'oijr. Distribution. France. Germany. Austria 

 and Galicia. Hungary. Italy. Norway. Sweden. 

 Denmark. Bornholm. Poland. N. Russia. Nova 

 Zenibla. Spitzbergen. Greenland. India. New 

 Zealand. United States. Brazil. Paraguay. 



Var. crassum Boldt. 



Pleurot&nium truncatum var. OMSSIM)/ lioldt, Siber. Chlorophy. 1885, 



p. 121, t. G, f. 4-1 ; West & G. S. West, Alya-fi. Yorks. 19UU, p. 59. 

 PI. Brcfddii Istvanffi, Diag. pru3v. A!LT. nov. Hangar. 1887, p. 24U. 



Cells shorter than in the typical form, only 4 times 



t/ 1 7 



Longer than their diameter; semicells more tumid, 

 without basal inflation, and without apical tubercles. 



Length 255 /A; maximum breadth (5o/z. 



Kxcii.vND. Gormire, N. Yorks (Turner). 



drot/r. Distribution. --Hungary. Sweden. Xova 

 Zembla. Siberia. 



Wo think that Boldt 's variety ini^lit perhaps IK- placed as 

 a specie's, l>ut as we have never seen a specimen of it- 

 cannot pronounce a definite opinion on this point. 



