220. BRITISH DESMIDIACE.E. 



those scrobiculations near the isthmus being disposed 

 in horizontal lines, the rest scattered; chloroplasts 

 with a median series of four or five pyrenoids ; semi- 

 cells in side view rather suddenly narrowed near the 

 apex. 



Zygospore globose, with a thick, smooth cell-wall. 



Length 138-230 /A; breadth 30-40 /A ; breadth of 

 isthmus 25 40 /A ; diam. zygosp. (5373 /A. 



ENGLAND. Cumberland ! Westmoreland ! (Haifa). 

 Lancashire ! (Rolfs). W., X., and E. Yorks ! Cheshire 

 (Hoi/). Leicester (Boy). Essex! Warwick (M7//x). 

 Gloucester (Ha .1 fa). Surrey! (Haifa). Sussex (Haifa). 

 Kent ! (Haifa). ' Hants ! (Ifalfa). 'Devon! Cornwall! 

 (If-d-lfa) ; zygosp. from Tintagel ! 



WALES. Common ! ; at 2,200 ft. on Glyder Facli, 

 and at 2,700 ft. on Glyder Fawr, Carnarvonshire. 



SCOTLAND. Abundant ! (Hui/ $ JH.wtt) ; zygospores 

 from Fyvie and Birsemore, Aberdeen ; Glen Dye, 

 Kincardine. Up to 3,500 ft. on Loclmagar ! Outer 

 Hebrides ! Orkneys ! Shetlands ! 



IRELAND. Abundant (zygosp. from Lough Anna, 

 Donegal) ! 



(Iroyr. Distribution. France. Belgium. Germany. 

 Austria and Galicia. Hungary. Italy. Portugal. 

 Norway. S \veden. Denmark. Bornholm. N. and 

 S. Russia. Iceland. Greenland. China. Ceylon. 

 Java. Australia. Sandwich Islands. Azores. United 

 States. W. Indies. 



T. yrunnlalns is the most abundant and generally distri- 

 buted species of Tetmemorus. It is a very cosmopolitan 

 species and occurs from sea-level to the snow-line, but rarely 

 in the freshwater plankton. In Sphagnum-bogs it sometimes 

 occurs in large quantities, and almost pure gatherings of it 

 can be obtained. It is a more slender and more attenuated 

 species than T. J>rt'l>i*N(iii, with a less conspicuous difference 

 between the front and side views, and a different arrange- 

 ment of the marks on the cell-wall. The specific name 

 " yranulatus " is somewhat unfortunate, as the cell-wall is 

 not granulate but finely scrobiculate, the scrobiculations being 

 the optical expression of pores through the cell-wall. 



