BRITISH DESMIDIE/E. 93: 



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

 notcli 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. cpiadratum is smaller than C. Cucmnis, 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 uiforms me that at the time I described C. quadratum in 

 the ' Armals 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 Js^ to 



36 2 3 ^^ 3 4 7 2' 



Tab. XV. fig. 1. a. front view; h. side ^dew ; 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. 



Cosmai'ium Cttcumis, Corda, Aim. de Carlsb. 1835, p. 121. f. 2/. Meneghini, 



Synop. Desmid. in Linncea 1840, p. 220. 

 Euastrum integerrimum, Ehr. In/its. p. 163. t. 12. f. 9. (1838), according to 



Meneghini. KUtzing, PhycoJogia Gei-manica, p. 136 ? 

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



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

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

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



Geimany, Corda, Ehrenberg, KUtzing. Falaise, BrSbisson. 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 -^^ to o-i^ of an inch ; breadth from y^^ to -g\^ ; 

 breadth at constriction from t-A-tt to , „' » . 



14 3^ 



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 ; transv.erse view fusiform. 



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

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

 Flora ofTunbridge Wells, p. 196. Hass. Brit. Algce, p. 366. (Not of 

 Corda according to Brebisson.) 



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



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



