]<>_! BRITISH DESMIDIACE/E. 



1'eniinn minutum (Ralfs) Cleve, Sverig. Desni. 1864, p. 41(3 ; Rabenh. 



Flor. Exu-op. Alg-ar. Ill, 18(58, p. 122; Lund. Desm. Suec. 1871, p. S7 ; 



Wolle, Desm. U. S. 1884, p. 35, t. 5, f. 19, 20 ; Wille, Sydamerik. Algfl. 



1884, p. 22 ; Eacib. Nonn. Desm. Polon. 1885, p. GO ; West, Alg. \V. 



Ireland, 1892, p. 129 (forma genuina) ; Liitkem. Desm. Attersees, 1893, 



p. 545 ; Norclst, Index Desm. 189(5, p. 172 ; West & G. S. West, Wehv. 



Afric. Freshw. Alg. 1897, p. 78 ; Alg. S. England, 1897, p. 479 ; Alga-fl. 



Yorks. 19< X>, p. 48 ; Alg. N. Ireland, 1902, p. 22 ; Freshw. Alg. Ceylon, 



I'.Kd, p. 136. 

 Pleurotxnium minutum Delp. Desm. subalp. 1877, p. 131, t. 20, f. 17-21 ; 



De Toni, Syll. Alg. 1889, p. 904. 

 Calncyli ml ni s minutus Kirchn. Alg. Schles. 1878, p. 142; Wolle, De.sm. 



U. S. 1884, p. 54, t. 12, f. 12. 

 Dysphinctium minutum Hansg. in Oesterr. bot. Zeitschr. 18S7, xxxvii, p. 



''j'.i : Pi lr. Algenfl. Bohm. 1888, p. isr>. 



Cells of medium size, elongate, 8-12 times longer 

 than their diameter, almost cylindrical, with a distinct 

 median constriction, very gradually attenuated towards 

 the apices, which are truncate ; cell-wall colourless, 

 smooth or minutely punctate ; chloroplasts variable, 

 generally axile with a central row of about 6 pyrenoids 

 and several irregular longitudinal ridges. 



Zygospore unknown. 



Length 9 7-1 68 ft; breadth 12-5-1 8 ft; breadth of 

 apices 8*5-11 ft. 



ENGLAND. Cumberland! Westmoreland ! (Bissett). 

 Lancashire! W., K, and E. Yorks ! Sussex (Ralfi). 

 Hants! Devon! Cornwall! (Marquand). 



WALES. General, but scarce ! 



SCOTLAND. General, but scarce! (Roy cj* Bissetf). 

 Common, in the Outer Hebrides and west of Scotland ! 



IRELAND. Generally distributed in the west and 

 south-west ! Donegal ! Londonderry ! Down ! Dublin 

 and Wicklow (Archer}. 



d'rngr. Distribution. France. Germany. Austria. 

 Italy. Poland. Russia. Norwav. Sweden. Ceylon. 



e . v 



West Africa. United States. British Guiana. Brazil. 



This Desmid is by no means common, although it often 

 occurs in abundance in the Sphafpnwm-loQgs of the western 

 parts of the British Isles. Its position in the genus Pein'nm 

 is questionable, but its position in any other genus would be 

 still more so. It was originally placed by Ralfs in Docidium, 

 from which genus, as now generally accepted, it must per- 

 force be excluded. 



