122 BRITISH DESMIDIACE^E. 



9. Closterium regulare Breb. 

 (PI. XIII, figs. 4-6.) 



CVds/ivmm regulare Bivb. Liste Desm. 185G, p. 148, t. 2, f . 35 ; Kabenh. 



Flnr Europ. Algar. Ill, 18(38, p. 12ti ; Nordst. Fivslnv. Alg. X. Zeal. 



is.ss, p. 78; K".v & Biss. Scott. Desm. 18<J4, p. 248 ; Nordst. Indrx 



Desm. 1896, p. 223; West &. G. S. West, Alg. S. England, IMC. 



p. 481 ; Freshw. Chluruphy. Koh Chang, 1901, p. 82. 

 Closterium striolatum a Klebs, Desm. Ostpreuss. 1879, p. 14, t. 2, f. 2. 

 Arthrudia regular is Kuntze, Kevis. gen. plant. 1891, p. 884. 



Colls of medium size, about '.> times longer than the 

 diameter, moderately curved, outer margin from 6(5 

 to 86 of arc, inner margin not tumid, gradually 

 attenuated towards the apices, which are somewhat 

 elongated and truncately or angularly rounded; cell- 

 wall pale yellow- brown in colour and costate, with 

 H-12costa3 visible across the cell; each chloroplast 

 with about 5 pyrenoids ; terminal vacuoles with a 

 number of moving granules. 



Zygospore unknown. 



Distance between apices 226-280 /x; breadth 24-oo/x; 

 breadth of apices 6-9 p. 



ENGLAND. Putteiiham Common, Surrey (small 

 forms) ! 



SCOTLAND. Near Kingshouse, Argyll (Roy fyBissett). 



Geoi/r. Distribution. France. Norway. Lapland 

 in Russia. India. Siam. Australia. West Africa. 



This rave species occupies a position intermediate between 

 Gl. costatuui and Cl. striolatum. It is distinguished from (In- 

 former by its somewhat smaller size, more attenuated apices, 

 and by the greater number of costte ; from the latter it differs 

 in its more attenuated and relatively narrower apices, and by 

 the presence of 11 or 12 visible costa? instead of 14 or more 

 striolations. The costi\3 of Cl. regulare are of about the same 

 strength as those of Cl. covtatiiiu, but ai*e much closer together ; 

 they are much stronger than the striso of Cl. striolatum. 



% 

 10. Closterium striolatum Ehrenb. 



(PL XIII, figs. 7-16.) 



striolatum Ehrenb. Entwick. Lebends. d. Inl'us. 1832, p. UN ; 

 Iiifus. 1838, p. 9(i, t. G, f. xii; Menegh. Synops. Desm. 1840, p. 231; 

 Hass. Brit. Frodhw. Alg. 1813, p. 371, t. 87, f. 4; lialfd, Brit. Dosm. 



