BRITISH DESMIDIE.C 163 



Chsterium tenue, Bailey, American Journal of Science and Arts, v. 41. p. 303. 



t. I. f^7 (1841)? 

 Closferimu lanceolatam, Kiitzing, Phycologia Germanica, p. 130 (1845), in 



fit. cum icone. Brebisson, in lit. 



About Lisburn ; and near Belfast, Mr. D. Moore. Galway, Mr. M'Calla. 

 Ambleside, Mr. Sidebotham. Westerham, Kent, Mr. Jenner. 



West Point, New York, Bailey. Germany, KUtzing. Falaise, Brebisson. 



Frond semilanceolate, six to ten times longer than broad ; stouter than that 

 of Closterium acerosmn ; lower margin straight, but inclined upwards at each 

 end owing to the tapering of the extremities ; upper margin convex ; fillets 

 three or more ; vesicles in a single longitudinal series. Empty frond usually 

 colourless and destitute of stride . 



Closterium lanceolatum is larger than C. acerosum ; instead of being nearly 

 alike, its margins, as stated above, differ considerably from each other, and its 

 extremities are more tapering. It is distinguished from C. Lunula by having 

 its vesicles in a single series, and its upper margin much less convex. Its ends 

 are neither curved upwards, nor so obtuse as those of C. turgidum. 



Length of frond -^ of an inch ; greatest breadth j-i-j • 



Tab. XXVIII. fig. 1. a. frond with endochrome ; b. empty frond. 



4. C. turgidum (Ehr.) ; lower margin of frond slightly concave, in- 

 clined upwards at the rounded ends ; upper margin with a depres- 

 sion near each extremity ; empty frond coloured ; striae numerous, 

 fine but distinct. 



Closterium turgidum, Ehrenberg, lufus. p. 95. t. 6. f. 7 (1838). Meneghini, 

 Synopsis Desmid. in Linncea 1840, p. 234. Jenner, Fl. of Tunbridge 

 Wells, p. 196. Kiitzing, Phycologia Germanica, p. 131. Hassall, 

 British Freshwater Algce, p. 3/1. 



Carnarvon ; Dolgelley ; Penzance, /. R. Sussex ; Kent ; Surrey ; Hamp- 

 shire, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Cheshire 

 and Westmoreland, Mr. Sidebotham. 



Germany, Ehrenberg . France, Brebisson. 



Frond stout, visible to the naked eye, green, six to ten times longer than 

 broad, semilanceolate ; extremities curved upwards, ends broadly rounded. 

 The lower margin is somewhat concave, but always sloped upwards at each 

 end, where the upper margin, which is convex, has a slight depression in 

 consequence of the inclination of the apex upwards. The vesicles form a 

 single longitudinal series ; fillets three or more. 



The empty frond is reddish or straw-colour, and somewhat opake ; the 

 suture at the middle is distinct, and so are the longitudinal striae, which are 

 numerous, close and fine. 



The curved and rounded ends are characteristic of this species. Closterium 

 decussatum, Kiitz., differs in its more attenuated extremities. 



Length of frond -^ of an inch ; greatest breadth 3^ ; distance between 

 the striae ^yW- 



Tab. XXVII. fig. 3. a. frond with endochrome ; b. empty fronds. 



M 2 



