188 BRITISH I>KSM[]i!.\('ME. 



the :irtii;il body of the ( 'loxfi'i-in t. bciiiL 1 ' pnp< irt \< m;il el y 

 smaller and the a pit-ill pnnvsscs relatively longer. It is 

 generally less curved than ('I. rnxl rat inn, and tin. 1 cell-wall 's 

 limn- conspicuously striated. The' a null's of the 

 are ul.so more rounded. 



Var. vittatum Nordst. (PI. XXV, figs. VJ, 1:>.) 



Cl. Ktit.zhi<iii var. vittahim Nordst. 1887; Freshw. Alg. N. Zeal, isss, 

 p. 70, t. 3, f. 21 ; De Toni, Syll. Alg. 1SS9, p. S5o. 



Cell-wall costate, about 5 or costse visible across 

 the cell. 



/vgospore precisely similar to that of the type. 

 Length 330-430 /A ; breadth 13'5-18/m. 

 ENGLAND. Near Goring, Oxford (with zygosp.) ! 

 (Jrnt/r. Dixtrihntinii-. New Zealand. 



'Phis is a very striking- variety which we- have only obtained 

 once-. The proportions of the vegetative cells and the Form 

 of the /ygospore arc exactly like those of typical Cl. Kid::i injii. 



V.. Closterium rostratum Ehrenb. 

 (PI. XXVI, figs. 1-5.) 



Ctosteriinii ,-<ixtr<ttnm Ehiviib. Entwick. Lobencls. d. Infus. 1S:?2, p. (17 : 

 Int'iis. ISliS, p. 97, t. 0, f. x ; Menegh. Synops. Desm. 1S1-O, p. 1'3-i ; Mass. 

 Brit. Froshvv. Altf. 18J.5, p. :V7:5, t, S7, f. ti; Kalf.s, JJrit, Dusiu. IM-s, 

 ]. 175, t. 30, f. 3 ; "De Baiy, Conj. 1S5S, p. 50, 54, t. 5, f. 20-30; Arch, in 

 1'riU-li. Infus. 1861, p. 749, t. 3, f. -14; KuViih. Flor. Europ. Alg. Ill, 

 ls(i,s, p. 135; Delp. Desm. subalp. Ls77. p. 118, t. 17, f. G3-6H /u ; Kirclm. 

 A.lg. Scldes. 1S7S, p. 1-1-1 ; Wolle, Desill. U.S. 18S-1-, p. 1(>, t. S, f. 1-3; 

 ( 'noke, Brit. Desm. 1880, p. 33, t, 11, f. 3 ; Hansg. Prodr. Algenfi. Bohiu. 

 ISSN, p. 183 ; De Toni, Syll. Alj. 1880, p. 851 ; West, Alg. W. Ireland, 

 18!)2, p. 125; Eoy & Biss. Seott, Desm. 18!)1, p. 218; Nordst. Index 

 Desm. IS'.Mi, p. 225; West & (.J. S. West, Al--. S. England, 181(7, p. -1-82; 

 Alga-H. Vorks. I'.iod, p. 57; Alg. N. Ireland, 1902, p. 21. 



Cl. Acus Nitzsch in Kiit/.. Syn. Diat. 1831, p. 595, t, 18, f. 81. 



Cl. caudatum (.'orda in Aim. d. Carlsbad. 1835, p. 19O, 209, t. a, f. 06. 



Cl. rnxl r.il inn a. lijp'n-tuii Kiel >s, Desm. Ostpreuss. 1879, p. 18. 

 rostrata Kuntze, Kevis. gen. plant. 1891, p. 881. 



(Vlls of medium size, 12-18 times longer than their 

 greatest diameter, slightly curved, median part of cell 

 fusiform-lanceolate, inner margin more convex than 

 outer margin, extremities prolonged into long, colour- 

 less processes which are slightly incurved, apices obtuse 



