194 JJR1TISH DESMIDIACEyE. 



Pen. (Dfx-iiliinii) Sceptrum Kiitz. Spec. Alg. 1849., p. 168. 

 PleurotsKniinn Hin-tihnu (Brcb.) Do Bary, Conj. 1858, p. 75; Delp. Desm. 

 sul.ulp. 1S77, p. 130, t, 20, f. 12-l(i. 



Cells small, narrowly snbcylindrical, 1-3-25 times 

 longer than their diameter ; semicells subcylindrical, 

 with a prominent basal inflation, which is plicated and 

 Furnished with a ring of basal granules (of which from 

 five to seven are visible across the cell), with a slight 

 constriction above the basal inflation ; oradviallv or 



O (/ 



sometimes scarcely attenuated from the middle of the 

 semicell to the apex, which is smooth and truncate ; 

 cell- wall smooth. 



Zygospore unknown. 



Length 148-262 (even up to 348) p.; breadth of 

 basal inflation O'5-lo p ; breadth of apex 4'S-IO^,. 



ENGLAND. Westmoreland ! (Raff*). W. and N. 

 Yorks ! Lancashire (li'<tl/x). Gloucester (Ralfs). Sussex 

 (Rttlf*). Hants! Cornwall (R.ilf*). 



WALES. Capel Curig ! ((.W,v $ TI7//.s), and near 

 Dolbadarn Castle ! , Carnarvonshire. Llyn Coron, 

 Anglesey ! 



SCOTLAND.- -Widely distributed, but scarce ! (Tlmj A;- 

 liixxcft state "general"). Not uncommon in the 

 Outer Hebrides ! 



IRELAND. Donegal ! Mayo ! Gal way ! Kerry ! 

 Dublin and Wicklow (Archer). Down ! 



(!t>nt/r. Distribution. France. Germany. Galicia 

 in Austria. Hungary. Italy. Portugal. Norway. 

 Sweden. Denmark. Born holm. N. and S. Russia. 

 India. Ceylon. Java. Madagascar. E. Africa. 

 United States. Brazil. Guiana. Paraguay. 



Although tins is the most frequent British species of the 

 o-euiis, it is nevertheless somewhat rare. It is rarely found 

 except in situations in which Desmids are abundant. 



2. Docidium undulatum Bail. 

 (PI. XXVII, figs. 7-10.) 



Dnriilinni int<1 iilnhtui I!;ul. Microscop. observ. ISfiO, p. ;!(i, t. 1, f. 2 ; Arch, 

 in 1'rilrh. Infus. 1 SSI , p. 7-15 ; Ealx-nh. Flor. Enrop. Al^ar. III. 1SC,S. 

 p. 1 !..->; !>c Toni. Syll A1-- iss'.l.]). S74: Tumor. Froshw. Al--. E. Inclia, 

 is'.i:;. p. ::.-,. t. l, 1. i(i. 



