BRITISH DBSMIDIE/E. 93 



Frond minute, constricted in the middle, the constriction forming a hnear 

 notch on each side. The segments are compressed, and in the front view nearly 

 square ; on each side of the base there is a slight protuberance. 



C. quadratuin is smaller than C. Cucumis, and its ends are not so rounded ; 

 but as these forms so nearly approach each other, it may prove to be merely a 

 variety. I have however seen no intermediate state, and have therefore kept 

 them distinct. 



M. De Brcbisson informs me that at the time I described C. qiiadratum in 

 the ' Annals of Natural History,' he had not only recognized it as distinct, but 

 had conferred on it the same specific name. 



Length of frond -^\^ of an inch ; breadth -^\-^ ; breadth at constriction 

 from -^-^^r^ to 



36 2 3 ^" 34 7 2" 



Tab. XV. fig. 1 . a. front view ; b. side view ; c. empty frond of variety. 



2. C. Cucumis (Corda) ; frond smooth^ deeply constricted at the 

 middle ; segments as broad as long and rounded at the end ; trans- 

 verse view broadly elliptic. 

 /3. segments semiorbicular. 



Cosmarium Cucumis, Corda, Aim. de Carlsb. 1835, p. 121. f. 27. Meneghini, 



Si/nop. Desmid. in Linncea 1840, p. 220. 

 Euastrum integerrhnutHy Ehr. Infus. p. 163. t. 12. f. 9. (1838), accordhig to 



Meneghini. Kvitzing, Phycologia Germanica, p. 136? 

 Pithiscus angulosus, KUtz. Phycol. Germ. p. 129 (1845). 



Midhurst and Fittleworth, Sussex, Mr. Jenner. Dolgelley and Penzance, 

 J. R. Near Bristol, Mr. Thwaites. Aberdeen, Dr. Dickie. Banffshire, 

 Mr. P. Grant. Ambleside, Mr. Sidebotham. 



Germany, Corda, Ehrenberg, Kiitzing. Falaise, Brebisson. United States, 

 Bailey. 



Frond minute, about twice as long as broad, compressed, quite smooth, 

 constricted at the middle, the constriction forming a linear notch on each side. 

 In a. the sides are nearly straight, except near the ends, which are rounded ; 

 but in /3. the sides also are rounded. 



C. Cucumis is smaller than C. Ralfsii ; its frond is not so orbicular, and 

 the transverse view is different. 



Length of frond from 3^ to -^^ of an inch ; breadth from -j-^-g- to -g-i-g '■> 

 breadth at constriction from , Z, a to , „' „ . 



1436 



Tab. XV. fig. 2. a. front view ; b. empty frond of var. /3 ; c. transverse view. 



3. C Ralfsii (Breb.) ; frond orbicular, smooth, deeply constricted at 

 the middle; transverse view fusiform. 



Cosmarium Cucumis, Ralfs, in Annals of Nat. Hist. v. 14. p. 395. t. 11. f. 8. 

 (1844) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 151. t. 16. Jenner, 

 Floi-a of Tunbridge Wells, p. 196. Hass. Brit. Algce, p. 366. (Not of 

 Corda according to Brebisson.) 



Cosmarium Ralfsii, Brebisson in lit. {cum icone) (1846). 



Dolgelley, ./. R. Bogs at Fisher's Castle near Tunbridge Wells ; Fittle- 



