116 BRITISH DESMIDIACE^E. 



Length 184-220 /x; breadth 88-100 ju; breadth of 

 isthmus 70-84 /x. 



ENGLAND.- -Near Bowness ! (Bissett) and Loughrigg 

 (Bennett), Westmoreland. Hawkshead, Lancashire ! 

 Henfield, Sussex (Rolfs). New Forest, Hants. 

 (Bennett). 



WALES.- -Near Swansea, Glamorganshire (Ralfs). 



Geogr. Distribution. France. Germany. Austria and 

 Galicia. Bosnia. Sweden. Italy. Denmark. Bornholm. 

 Poland. S. Russia. Japan. Australia. New Zealand. 

 Patagonia (form). 



C. turgidum is one of the largest and most characteristic 

 species of the genus. We have only observed it in abundance 

 from near Bowness, Westmoreland. 



The parietal band-like cliloroplasts are sometimes con- 

 tinuous from end to end of the cell. 



Var. subrotundatum West. (PL LXXV, fig. 4.) 



C. turgidum var. subrotundatum West, Alg. Engl. Lake Distr. 1892, p. 729. 



Cells about twice as long as broad ; semicells inflated 

 and subcircular. 



Length 140 ^ ; breadth 77 /*; breadth of isthmus 60 /x. 

 ENGLAND.- -Bowness, Westmoreland ! 



Schmidle has suggested that the outline of this form was 

 due to distortion underpressure (vide Schmidle in ' Hedwigia/ 

 xxxiv, 1895, p. 73). Many Desmids possess cell-walls suffi- 

 ciently elastic to exhibit considerable distortion under pressure 

 before they rupture at the isthmus. This variety, however, 

 does not owe the rounded form of its semicells to such a 

 cause. It was most likely produced by vegetative cell-division, 

 as we have observed several young semicells of a similar out- 

 ward shape which have undoubtedly arisen as a result of 

 abnormal cell division. Consult also Delp. 'Desm. subalp/ 

 1877, t. 21, f. 5 ! 



125. Cosmarium subturgidum (Turn.) Schmidle. 



(PL LXXV, fig. 5.) 



Dysphinctium subturgidum Turn. Fresliw. Alg. E. India, 1893, p. 40, 



t. 7, f . 4. 

 Cosmarium subturgidum (Turn.) Schmidle, Alg. aus Sumatra, 1895, 



p. 300. 



