BRITISH DESMIDIE^. 157 



Segments eight to twelve times longer than hroad, gradually thickened near 

 the ends in a clavate manner, the end itself being slightly attenuated and 

 truncate ; there is a single inflation at the base. Vesicles small, few, and 

 arranged in a single longitudinal line. The empty frond is minutely punctate, 

 but the highest powers of the microscope are required to detect the puncta. 



Breljisson's specimens are more clavate than British ones, or than Kiitzing's 

 plant appears in a drawing received from him. 



Length of frond ^ of an inch ; breadth -g-^ ; breadth at inflation -gig ; 

 breadth at end y-aVj- 



Tab. XXVI. fig. 3. a. frond with endochrome ; b. empty frond from French 

 specimen. 



4. D. Ehrenberyii ; segments many times longer than broad, 



having two or three slight inflations at the base and truncate ends 

 bordered by minute tubercles. 



/3. granulatum ; frond rough with minute granules. 



Closterium Trabecula, Ehr. Ahh. d. Berl. Ak. (1830), p. 62; Infus. p. 93. 

 t. 6. f. 2. Meneghini, Synop. Desmid. p. 235. Kiitzing, Phycologia 

 Germanica, p. 133? Jenner, Flora of Tunbridge Wells, p. 196. 



Dolgelley, Carnarvon, Penzance, &c., J. R. Several stations in Sussex ; 

 and near Southampton, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. 

 Grant. Ambleside, Mr. Sidebotham. 



/3. Henfield, Sussex, Mr. Jenner. Penzance, J. R. 

 Germany, Ehrenberg, Kiitzing. Falaise, Brcbisson. 



Frond as long as those of Docidium nodulosum and D. truncatum, but far 

 more slender, constricted at the middle ; the suture strongly marked, but 

 having no projection at the margins. Segments eight to twelve times longer 

 than broad, having about two slight inflations at the base, but otherwise linear. 

 The end is truncate, and three to five minute tubercles, which may be detected 

 at its margin, give the end \iew a crenate appearance. The empty frond is 

 punctate, but in general the puncta are not readily discerned. Mr. Jenner 

 finds in Sussex a variety the frond of which is distinctly granulate. 



I have gathered the sporangia at Penzance for two successive years ; they 

 are large, suborbicular or elliptic, but often slightly angular, and are situated 

 between the conjugating fronds, from which they easily separate. 



Docidimn Ehrenbergii in size equals D. clavatum, but it is not clavate, and 

 its ends are bordered by minute tubercles. In the latter character it cor- 

 responds with D. coronatum, Breb. ; but it is much smaller and the suture 

 does not project at the sides. 



Length of frond from ^^ ^o s^V ^^ ^^^ "^^^^^ 5 breadth from y^Vr ^^ tst '■> 

 breadth at inflation from g^ to -g-iy ; breadth at end y^Vr 5 diameter of 

 sporangium -^. 



Tab. XXVI. fig. 4. a. frond with endochrome ; h. dividing frond ; c. empty 

 frond ; d. conjugating fronds ; e, f. sporangia. 



Tab. XXXIII. fig. 4. empty frond of variety ft. 



