rWSTERIVM. 12') 



1 1 . Closterium intermedium Ralfs. 

 (PI. XIV, figs. 1-5.) 



Closterium intermedium Ralfs, Brit. Dcsm. 1848, p. 171, t. 29, f. 3 and 

 f. 2 h- Arch, in Pritch. Infus. 1861, p. 749; Lund. Desm. Suec. 1871, 

 p. 77 ; Cooko, Brit. Desm. 1886, p. 29, t. 11, f. 2 ; t. 15, f. 6 ; Gxvtw. Flor. 

 Glon. Okolic Lwowa, 1891, p. 34 ; West, Alg. Eng. Lake Distr. 1892, 

 p. 720; Eoy & Biss. Scott. Desm. 1894, p. 245; Nordst. Index Desm. 

 1896, p. 148 ; West & G. S. West, Alg. S. England, 1897, p. 482 ; 

 Alga-fl. Yorks. 1900, p. 55 ; Alg. N. Ireland, 1902, p. 24; Freshw. Alg. 

 Ceylon, 1902, p. 137. 



? Cl. subjimcidum De Not, Desm. Ital. 1867, p. 63, t. 7, f . 68. 



Cl. striolatiim b. elongatum Rabenh. Flor. Enrop. Algar. Ill, 1868, p. 125 ; 

 Kirchn. Alg. Schles. 1878, p. 139 ; Hansg. Prodr. Algenfl. Bohm. 1888, 

 p. 242. 



Cl. subdirectum West, Desm. Massachusetts, 1889, p. 17, t. 3, f. 16. 



Arthrodia intermedia Kuntze, Revis. gen. plant. 1891, p. 884. 



Cells of medium size, 12-15 times longer than their 

 diameter, moderately curved, outer margin from 36 to 

 45 of arc, inner margin slightly concave, not tumid but 

 sometimes straight in the median portion, gradually 

 attenuated towards the apices, which are truncate with 

 rounded angles ; cell-wall pale yellow or yellowish- 

 brown in colour, strongly striated, with 8-10 visible 

 striae across the cell ; each chloroplast with 5 or 6 

 pyrenoids; terminal vacuoles with one large moving 

 granule or a few smaller ones. 



Zygospore globose and smooth. 



Length 234-465 /A; breadth 16-31 /A; breadth of 

 apices 10-11 '5 /A; diam. of zygosp. 38-54 /x. 



ENGLAND. Cumberland! Westmoreland ! (Bissrtt). 

 W., N., and E. Yorks ! Cheshire (Pot/). Leicester 

 (Ro;/). Warwick (Wills). Surrey! Hants (liny). 

 Devon! (Bennett}. Cornwall! (Marquand). 



WALES. Bettws-y-coed (Roy), Capel Curig ! (CW.r 



Wills)., Glyder Fawr (Roy), near Dolbadarn Castle ! , 

 Llyn Paclarn, Carnarvonshire ! Dolgelly, Merioneth 

 (Ralfs). 



SCOTLAND. Sutherland ! , Ross, Inverness ! , Nairn, 

 Aberdeen, Kincardine, Forfar, Perth ! , Stirling, Dum- 

 barton, Argyll, Renfrew, Arran; zygospores f rom Fyvie, 

 Aberdeen (Roy Bissett). Kirkcudbright ! Lewis, 

 Harris, and Benbecula, Outer Hebrides ! Orkneys ! 



