fLOSTERHTM. 147 



Cl. acerosum A. majus Eeinseh. Algenfl. Frank. 1867, p. 186. 



Cl. acerosum a. typicum Klebs, Desin. Ostpreuss. 1879, p. 7, t. 1, f. 6. 



Cl. acerosum var. trum-nl K,H (Jutw. Wahr. <l. Prioritfil, is; in. p. ii(; ; Flor. 



Glon. Okolic Lwowa, 1S91, p. 33, t. 1, f. 7 ; West & G. S. \\Vs1 , Al^i-fl. 



Yorks. 1900, p. 52. 

 Arthrodia acerosa Kuntze, Eevis. gen. plant. 1891, p. 883. 



Cells large, 8-16 times longer than their diameter, 

 very slightly bent or almost straight, narrowly fusiform, 

 outer margin slightly curved (about 10-20 of arc), 

 inner margin almost straight or slightly convex ; semi- 

 cells gradually tapering to the apices, which are narrow 

 and rounded-truncate (often slightly thickened) ; cell- 

 wall colourless and smooth, in older individuals becom- 

 ing yellowish-brown and very delicately striolate ; 

 chloroplasts ridged, with a median series of 7-11 

 pyrenoids ; terminal vacuoles with a number of moving 

 granules. 



Zygospore globose and smooth. 



Length 300-460 /u, ; breadth 26-48 //, ; diam. zygosp. 

 62-87 ft. 



ENGLAND. - -Westmoreland ! (Ralfi). W. (with 

 /vgosp.), N., and E. Yorks ! Lancashire ! (Ruffs'). 

 Cheshire (Ralfx). Leicester (Roy). Essex! Cam- 

 bridge ! Oxford ! Warwick (Wills). Gloucester 

 (Raffi). Middlesex (with zygosp.) ! Surrey ! (Rolfs). 

 Sussex (Rolfs). Kent! Hants! Devon! Cornwall! 

 (Ralfs). 



WALES. General ! 



SCOTLAND. Widely distributed, but scarce ! (Roy fy 

 Plankton of Loch Asta, Shetlands ! 



IRELAND. Galway ! Kerry ! Dublin and Wicklow 



rcJtc'i'). Down! Antrim! 



Geo//r. Distribution. France. Germany. Austria 

 and Galicia. Hungary and Bosnia (var.). Italy. Spain. 

 Portugal. Norway. Sweden. Denmark. Born holm. 

 N. Russia. Iceland. Nova Zembla. Greenland. 

 Siberia. Manchuria. Japan. India. Ceylon. Siam. 

 Australia. New Zealand. United States. Mexico. 

 Brazil. Ecuador. Patagonia. 



Cl. acerosum is a common species and often occurs abun- 

 dantly amongst larger filamentous Alga?. The cells frequently 



