I'LoSTKK'ir.M. 177 



and colourless ; chloroplasts with four or five pyre- 

 noids; terminal vacuoles remote from the apex, \\illi 

 one moving grannie. 



O O 



Zygospore globose and smooth. 



Length L10-260/x; breadth <'-<>:> p. 



E\(.M,\\I. Helvollyn, Westmoreland ! Mickle Fell, 

 X. Yorks! Delamere, Cheshire (.Ro?/). Wimbledonand 

 Esher Commons, Surrey ! Enbridgr Lake, Hants (L'<>//). 



SCOTLAND. General but scarce; zygospores from 

 Seotston Moor and Sle\vdrnm, Aberdeen (ti<n/ <j* 

 Bissett). 



[BELAND. Plankton of Lough Neagh ! 



(ii'injf. Distribution. France. Germany. Switzer- 

 land. Austria and dlalicia. Sweden. 



We always find the apices of this species to be drawn out 

 into fine, almost bristle-like points. They are, in fact, the 

 sharpest apices met with in the whole of the genus. lialten- 

 lioi-st also describes the apices as " aciit issimis, liyalinis," but 

 continental observers have recorded under the name " 01. 

 Ceratium," specimens with relatively obtuse extremities. 



Ft is nearest to 01. -print inn P>reh., from which it is distin- 

 guished by its relative shortness, by the variable curvature 

 of the cell, and by the much sharper and more produced 

 apices. 



51. Closterium acutum (Lyngb.) Breb. 

 (PL XXIII, figs. 9-14.) 



Erliinella acuta Lyn^byc, 1819. 



FriixtuJiii uriitn Kiitz. Syn. Diat. 1S34, p. 537. 



Closterium (.'ii?i-i-lnuim Kiitz. Phyc. ^cnn. 1845, p. 130. 



Closteriuin m-ntum Bveh. in Rail's' Jlrit, Dosin. 1848, p. 177, t. 30, f. 5, 



t. 34, f. 5 a, b, tl-f; Do Bary, Conj. 185,8, p. 41, t. 5, f. 13; Eabenh. 



Flor. Europ. Algar. Ill, ISlis, p. 137 ; Kirchn. Alg. Schles. 1878, p. 140 



Wolle, Dosni. U.S. 1884, p. 44, t. 7, f. 11, 12; Cooke, Brit. Desiu. Jssii. 



p. 35, t. 14, f. 5; Do Toni, Syll. Alg. 1889, p. 836; West, Alif. W. 



Ireland, 1892, p. 125; Al#. Eng. Lake Distr. 1892, p. 720; Koy & Biss. 



Scott. Desiu. 1894, p. 243 ; Nordst. Index Desui. 1896, p. 39 ; West & 



G. S. West, Alo-. S. England, 1897, p. 482; G. S. West, Als?a-fl. Cam In- 



1899, p. 113 ; West &. G. S. West, Alga-fl. Yorks. 1900, p.' 56 ; Alg. N. 



Ireland 1902, p. 25. 



Stauroceras m-tita Grun. Desm. IT. Podiast. osterreich. Moore, 1858, p. 1!)7. 

 Closterium pronum Breb. b. acutum Klebs, Desm. Ostpreuss. 1879, p 19 



t. 2, f . 12 b, 13 c. 

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



Cells small, 20-33 (rarely 15) times longer than 



12 



