Mr. J. Ralfs on the British Dcsmidicac. 405 



sometimes the cells seemed only held together by the hyaline 

 matrix, in which state they aj)pear to connect the DcsmidietB, 

 throutrh Gonidium, Ehr., and Trocldscia, Kutz., with the UlvaceeE. 



The cells of one row arc scpai-ated by the interposition of the 

 broader ends of the other. 



Plate XII. fig. 8. Sccnedesmns obtitsiis. 



Desmidium*, Ag. {Kutz.) 



Filaments elongated, triangular or quadrangular, regularly twisted, 

 fragile ; the joints bidentate at the angles. 



In my former jiaper on Desmidium I removed from that genus 

 all Ehrenberg^s species which do not form a filament, and re- 

 tained in it only those Desmidiece which have elongated jointed 

 filaments. Since its publication, Kutzing, in his ' Phycologia Ge- 

 neralis,' has restricted the genus to the species with triangular 

 filaments, and as this arrangement meets with the ap])r()bation of 

 Mr. Berkeley, I am induced, in deference to their joint opinion, 

 to follow it in the ])resent article, with a slight alteration of tlie 

 character which will enable me to include the plant described 

 below. 



The transverse view is triangular or qiiadrangxdar, and the en- 

 dochromc has in one case three and in the other case foui* rays ; 

 these are frequently cloven. 



1 . D. Swartzii, Ag. Filaments tiiangular, equal, with a single lon- 

 gitudinal, waved, dark line formed by the third angle ; end view 

 triangular with the cndochrome three-rayed. Kutz. Phycol. Ge- 

 neralis, p. 165 ; Mcnegh. Synop. Desmid. in Linna?a 1840, p. 203 ; 

 Ralfs in Annals of Nat. Hist. vol. xi. p. 375. pi. 8. fig. 3. 



I have only to add to my former notice of this plant, that it 

 has since been gathered near Cheshunt by Mr. Hassall, and in 

 many stations in Sussex by Mr. Jenner, also in Caragh Lake, 

 Kerry, by Mr. Andrews. 



2. D. quadrangulatum. Filaments quadrangidar, varying in breadth 

 from the twisting of the filament, and having two longitudinal, 

 waved, dark lines ; the end view is quadrangular, with the endo- 

 chrome four-rayed. 



In a boggy pool at Rologas near Penzance. 



Mr. Berkeley and ]\Ir. Borrer regard this plant as a variety of 

 D. Sicartzii, nor can I find any distinctive mark except those 

 which depend upon the filament being quadrangular in one case 

 and triangular in the other ; but Mr. Jenner informs me that the 



* Read before the Botanical Society of Edinburgh, July 11, 1814. 



