16 BRITISH DESMIDIACE^:. 



narrowly linear with a dilated extremity ; semicells 

 pyramidate with a truncate apex and sinuate margins, 

 sometimes almost five-lobed ; basal angles broadly 

 rounded, rounded-rectangular, or even ret use ; lateral 

 margins with two hollows, sometimes slight and some- 

 times fairly deep, often unequal ; apical part of cell 

 standing out as a polar lobe, subtruncate at the apex 

 with rounded angles, and with a deep linear incision in 

 the middle ; semicells with three protuberances across 

 the base and two across the middle. Side view of semi- 

 cell elongate-pyramidate, basal angles subrectangular, 

 somewhat wider above the base, then tapering upwards 

 to the apex, which is truncate with rounded angles. 

 Vertical view elliptical, with three protuberances on 

 each side, the two upper protuberances which show in 

 the middle of the lateral margin alternating with the 

 three lower ones ; polar lobe broadly elliptic. Cell- 

 wall punctate. 



Zygospore globose, furnished with numerous, blunt, 

 somewhat curved papillae. 



Length 130-195 /x; breadth 70-91^; breadth of 

 isthmus 16-27 ft ; thickness 42 45 /A; diam. zygosp. 

 without papillae 73'6-86/u,; length of papillae 9-13 p. 



ENGLAND. Cumberland ! Westmoreland (at 2,400 ft. 

 on Helvellyn) ! (Rolfs). W. and X. Yorks ! Lancashire 

 (zygospores from near Wrynose) ! Leicestershire 

 (Roii). Wilts ! Warwick (Wills). Surrey ! Sussex 

 (Rolfs); Kent ! (Rolfs). Hants ! (Rolfs}. Devon ! 

 (Bennett). Cornwall! (Rolfs). 



WALES. Fairly general ! 



SCOTLAND ! General ! (Roy $ Bissett). Zygospores 

 at Dalwhing near Aboyne, Aberdeen (Roy Bi-ssett). 

 Common in Outer Hebrides ! Orkneys ! 



e/ 



IRELAND. Donegal ! Mayo ! Gal way ! Kerry ! 

 Dublin and Wicklow (Archer). Zygospores from 

 Carrick Mountain (A rclter). Down! Londonderry! 



Geogr. Distribution. France. Germany. Austria 

 and Galicia. Italy. Norway. Sweden. Denmark. 

 Bornholm. Finland. Poland (var). X. and S. Russia. 



