620 



12. Closterium aciculare T.West 1 . 



The accompanying figure represents a Closterium which occur- 

 red fairly abundantly in a sample I gathered in thc small lake in 

 Kvanhauge 011 Sydero. I think il is identical wilh Cl. aciculare 



T.West, and Dr. Nordstedt is also of this opinion. It attains lo 

 a length of at least 450 /t, and the breadth varies with an average 

 of 5 /<. It has numerous pyrenoids, often upwards of 20. The cells 

 are sometimes slightly bent at both apices; sometimes the apices 

 are almost straight; sometimes individuals are met with which are 

 actually sigmoid. 



Of forms related to this species Cl. subpronum W.West 2 comes 

 so near to it, that it is not possible for me to find any character, 

 by which it may be distinguished. W.West writes with reference 

 to it (l.c): »In relative length and breadth this species agrees with 

 Cl. aciculare T. West, but is somewhat smaller, and does not begin 

 to laper until half-way from the centre to the apices, which are 

 nol »very acute««. But here I may remark that if we look al 

 W. Wesl's ligure ol Cl. subpromim, especially the one more highly 

 magnified (lig. 3 a'), il will be seen that it tapers evenly, right from 

 the centre; and when, moreover, T.West writes »very acute« then 

 this description agrees with the species known al that time with 

 which T. West compares Cl. aciculare; and if we compare the 

 figure of T. West with that of W. West it will be seen that the 

 apices of their semi-cells are in faet of the same thickness. As re- 

 gards the size, W.West mentions that Cl. subprouum is 427// long 

 and 3,7 j« broad ; but in a paper recently published 3 he piaces il 

 respectively 392—406 \i long and 4,2 — 5,2 /< broad, and the size ol 

 a var. lacustre referred by Leminermann 4 to this species is given 

 as 500 — 800 fi long and 6 — 8 // broad. In Sylloge Algarum Vol. 1, 

 p. 837, De To ni gives Cl. aciculare as 500// long and 5 /< broad; 

 the shortest individual which I have figured is 324 /< long; Ihe 

 Iongest 450/«, bul slill longer specimens doubtless occur. As nol 



1 West. Tuffen: Remarks on some Diatomaceæ, new or imperfectly iles 

 cribed, and a new Desmid (Quarterly Journal of Microscopical Science, Vol. VIII, 

 1860, p. 153, PI. VII, fig. 10). 



2 West, William: New British Freshwater Algæ (Journal of the R. Micro 

 scopical Society. lcS94, p. ',\, pi. 1, iig. 3). 



; West, W. and West (i. S.: A Contribution to the Freshwater Algæ of the 

 North of Ireland (Transactions of the R. Irish Academy, Vol. 32, Sect. 1>. Part. I. 

 1902, p. '->;>, pi. 2. li-s. 1 2). 



1 Lemraermann, E.: Planktonalgen, l.c. p. 344, pi. 1, figs. 13 — 14. 



