172 BRITISH DESMIDIE^. 



gustatum ten or twelve. The most remarkable feature in this plant is the 

 number of its sutures exceeding that of any other species ; it is more slender 

 and tapers more gradually than C striolatum. Its more numerous striae and 

 tapering form distinguish it from C. angustatum. 



Length of frond from y^ to -^ of an inch ; greatest breadth y^ts ! distance 

 between the strise yxstt- 



Tab. XXIX. fig. 3. a. frond with endochrome ; b, c. empty fronds, 



15. C. angustatum (Kiitz.) ; frond sublinear, curved^ scarcely attenu- 

 ated ; ends truncate ; striae few, very distinct and prominent ; 

 sutures usually three. 



Closterium angustatum, Kiitzing, Phycologia Ger^nanica, p. 132 (1845); in 



lit. cum icone. 

 Clostei'ium sulcatum, Brebisson, in lit. cum icone (1845). 



Dolgelley, J. R. Waterdown Forest, &c., Sussex ; Reigate, Surrey, Mr. 

 Jenner. Aberdeenshire, Mr. P. Grant. Ambleside, Mr. Sidebotham. 



Germany, Kutzing. Falaise, Brebisson. 



Frond cui-ved, eight or more times longer than broad, nearly equal in 

 breadth except towards the extremities which are somewhat attenuated, their 

 ends however being truncate. The vesicles are arranged in a single longitu- 

 dinal series ; fillets obscure. 



The empty frond is of a pale reddish colour and darkest at the ends. Trans- 

 verse sutures usually three, the central one of two or more lines. The longitu- 

 dinal striae, of which seldom more than three or four can be seen at one view, 

 are few in number, very distinct and prominent, and not unfrequently some- 

 what spiral. The frond, I believe, has several angles or ridges, which imder 

 the glass have the effect of striae. 



Its linear form and scarcely attenuated extremities distinguish this species 

 from Closterium intermedium. The striae also are fewer in number, less 

 crowded, and more distinct. C. angustatum diifers from C. juncidum by its 

 stouter form and more distinct striae ; its upper margin also is convex, and 

 not straight as in that species. 



Length of frond gL of an inch ; greatest breadth -^^xi 5 distance between 

 the striae g^Vo- 



Tab. XXIX. fig. 4. a. frond with endochrome; b, c. empty fronds. 



16. C. juncidum ; frond elongated, very slender, linear, straight 



except at the extremities, which are slightly attenuated and curved 

 downwards. 



/3. Frond stouter and less elongated. 



a. Dolgelley and Penzance, J. R. Chiltington Common near Pulborough, 

 Sussex, Mr. Jenner. Aberdeenshire, Br. Dickie and Mr. P. Grant. Amble- 

 side, Westmoreland ; and Congleton, Cheshire, Mr. Sidebotham. 



/3. Dolgelley, /. R. Midhurst, Sussex, Mr. Jenner. 



Falaise, Brebisson. 



Frond many times longer than broad, very slender, linear, straight except 



