CLOSTEEIUM. 133 



r. Distribution. Austria. Ceylon. Madagascar. 

 E. Africa. 



This species is distinguished from Cl. Dinn;r by its curva- 

 ture iind its smaller si/e. The apices are also relatively 

 narrower than in CL Dlanx, although according to Roy they 

 possess the oblique thickening found in that species. Tin's 

 character is, however, variable in (./. Pseudodianas, and is 

 often entirely absent. 



It is a very rare species of the genus except in certain areas 

 of the north-west of Scotland. The Austrian specimens 

 recorded by Lutkemuller are of somewhat smaller size and 

 have broader apices. 



16. Closterium parvulum Nag. 

 (PI. XV, figs. 9-12.) 



Closterium parvulum Niig. Gatt. cinz. Alg. 1849, p. 106, t. 6 C, f . 2 (in part) ; 



De Bary, Conj. 1858, p. -41, 42, 48-51, t. 5, f. 14-23 ; Kabenh. Flor. 



Europ. Alg. Ill, 1868, p. 134 ; Kirchn. Alg. Schles. 1878, p. 141 ; Wolle, 



Deam. U. S. 1884, p. 45, t. 7, f. 7, t. 8, f. 16 ; Hansg. Prodr. Algenfi. 



Bohni. 1888, p. 182 ; De Tom, Syll. Alg. 1889, p. 841 ; Liitkem. Desm. 



Attersees. 1893, p. 543; Koy & Biss. Scott. Desm. 1894, p. 247; West 



\ '<;. S. West, New and Int. Fresh w. Alg. 1896, p. 151; Nordst. Index 



Desm. 1896, p. 196; West & G. S. West, Alg. S. England, 1897, p. 481 ; 



(r. S. West, Alga-fl. Cambr. 1899, p. 112; West & G. S. West, Alga-fl. 



Yorks. 19UO, p. 49 ; Alg. N. Ireland, 1902, p. 23 ; Scott, Freshw. Plank- 



ton, I, 1903, p. 525. 

 Artli rnilin jnirriilii Kuntze, Eevis. gen. plant. 1891, p. 884. 



Cells small, 9-15 times longer than their diameter, 

 strongly curved, outer margin 120-140 of arc, inner 

 margin not tumid, gradually attenuated to the apices, 

 which are acutely rounded ; cell-wall smooth and 

 colourless (rarely yellowish-brown) ; chlorophists with 

 about five ridges and a single series of 36 pyrenoids ; 

 terminal vacuoles with several moving granules. 



Zygospore ellipsoid or subglobose, smooth. 



Distance between apices 96-121 JJL; breadth 11-14'5/x; 

 breadth of apices about 1'5/x; length of zygospore 

 30-40 /A ; breadth of zygospore 26-34*5 /x. 



ENCLAXI*. Cumberland I Westmoreland (with zy- 

 gosp.) I W. (with zygosp.), N. (with zygosp.), and E. 

 Yorks! Lancashire! Essex! Cambridge! Middle- 

 sex! Surrey (with zygosp.) I Kent! Hants! Devon! 

 Cornwall (with zygosp.) ! 



