BRITISH DESMIDIE.E. I7I 



p. 95. t.6.f. 12. Meneghini, Synopsis Desmid, inLinncea 1840, p. 234. 

 Bailey, Amer. Journ. of Science and Arts, v. 41. p. 303, t. 1. f. 35. 

 Kiitziiig, Phycologia Germanica, p. 131. Jenner, Fl. of Tunhridge 

 Wells, p. 196. Hassall, Brit. Freshioater Algce, p. 3/3. 



Common. Carnarvon ; Dolgelley ; Tal Sarn near Lampeter ; near Car- 

 marthen ; and Penzance, J. R. Sussex ; Surrey ; Kent ; and Hampshire, 

 Mr. Jenner. Kerry, Mr. Andrews. Galway, Mr. M'Calla. Hertfordshire, 

 Mr. Hassall. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Cheshire and 

 Westmoreland, Mr. Sidebotham. Manchester, Mr. Gray and Mr. Wil- 

 liamson. 



Germany, Ehrenberg . New York ; and New England, Bailey. Falaise, 

 Brebisson. 



Frond six to twelve times longer than broad, very variable in both length 

 and breadth, curved, tapering from the middle ; ends very obtuse ; upper 

 margin convex ; lower concave or straight, but never inclmed upwards at the 

 ends. Vesicles in a single series ; fillets often obscure. This species forms 

 yellovrish-brown masses in the water. 



The empty frond is reddish and darkest at the ends. Striae numerous, 

 crowded, and easily detected. Sutures usually three, but sometimes only two : 

 specimens with a single suture are very rare. 



The sporangia, which are not uncommonly met vd\\\, are orbicular and placed 

 between the deciduous fronds. 



Closterium striolatum is shorter than C. turgidum, and the ends do not turn 

 up ; its striae are much more numerous and close than those of C. costatum ; 

 and both C. turgidum and C. costatum have constantly but a single suture. 

 It is more closely striated than either C. intermedium or C. angustatum, and 

 stouter also in proportion to its length. With this species C. didymotocnm 

 in some respects agrees as to its size and form, but it is straighter and less 

 tapering, and its ends are more truncate, and the striae, if present, are detected 

 with the greatest difficulty. 



Length of frond from -g^ to -^-^ of an inch ; greatest breadth from ^y to 

 -g-i-5- ; distance between the striae Yo'.oo'o' 



Tab. XXIX. fig. 2. a, b, c. fronds with eudochrome ; d, e,f. empty fronds ; 

 g, h. sporangia. 



14. C. intermedium ; frond slender, slightly curved, tapering ; 



striae distinct, not crowded ; sutures usually more than three. 

 Dolgelley, J. R. 



Frond slender, nearly straight, many times longer than broad, very gradu- 

 ally tapering, ends truncate. Fillets obscure ; vesicles in a single series. This 

 species forms in the water large masses of a yellow-bro-mi colour. 



The empty frond is straw-colour ; its striae are distinct and can be counted 

 without difficulty. Sutures, though occasionally but three, are usually from 

 four to seven in number. The central suture often forms a pellucid line re- 

 sembling a dissepiment. 



In its form and in the number of its striae Closterium intermedium is inter- 

 mediate between C. striolatum and C. angustatum. According to M. de Bre- 

 bisson, C. striolatum has about forty striae, C. intermedium twenty, and C. an^ 



