166 ISUT1SH DESM1DIACE/E. 



gradually attenuated to the apices, which are somewhat 

 in curved and subacute; cell-wall smooth and colmirlc^ : 

 cliloroplasls with a central row of 7 or <S pyrenoids ; 

 terminal vacuoles with several moving grannies. 



Zygospore ellipsoid and smooth. 



Length ir>l<-:558 /x; breadth l-t-18'5 ,x. 



ENGLAND. - Scam lair, Westmoreland ! Rawcliffe 

 Common, W. Yorks ! Enbridge Lake, Hants (//"//) 



SCOTLAND. Near Tain and Strathpeffer, Ross ; Brin, 

 Inverness ; St. Fergus Canal, Mintlaw, Alford, White- 

 stt'ipes, Danestone, and near Spring-hill, Aberdeen; 

 Lochs of Park and Luingair, Kincardine (Roy fy 

 Biswft). Glen Shee, Perth \ 



IRELAND. Dublin and AVicklow (Arcln } r). Clough, 

 Antrim ! 



Gt'uf/i'. Distribution. France. Grermanv. Switzer- 



v 



land. Austria and Galicia. Hungary. Sweden. Poland. 

 N. Russia. Central and E. Africa. Brazil. 



The nearest species to CL strigosum is (.'/. /n'raci'i-uxinii- (Jay, 

 and it is indeed a doubtful question whether the latter species 

 should not really be placed under the former. Cl. /nrmv/v/.v/o// 

 is somewhat smaller in size, is relatively shorter, and has not 

 the characteristic incurved apices of Cl. strigosum. 



It seems very probable that various authors have confused 

 these two specie's of Closterium. The measurements ^iveii 

 by Ijiindell (l)esm. Suec. 1871, p. 7 ( J) of CL. strigosum, viz. 

 length 160-240 /<, breadth 10-10 /t, lead one to suppose 1 I hat 

 very possibly he had Cl.peracerosumund.er observation at the 

 time. Similarly, the measurements given by Kichler (Mai. 

 llor. Miedz. iSUo, }). ")<S), viz. length 145 ju, breadth 11 ^, are 

 much smaller than the average for Cl. strigosum. 



Wolle has described zyi^ospores which he believed to be of 

 this species, but as his figures ari' not j^'ood, and as he was 

 somewhat doubtful with regard to tlu i identification of his 

 specimens, the observation requires confirmation. 



43. Closterium gracile Breb. 

 (PL XXI, figs. 8-12.) 



Clostei-iinik '/i-'irilc Mivl). in Cheval. Des microscop. ct di- Icur USHL;V, 1'aris, 

 1839, p. 272; Kiilf.s, Brit. Dusni. 1848, p. 221 ; Itivl.. List,' LK-sni. 1856, 

 1>. I.")."), t. '2, f. 4-j ; Arch, hi Fritrli. Inl'iis. ISiil, p. 748; Kirchii. Aly. 



