62 BRITISH DESMIDIE^. 



thickened margin, which partly fills the notch formed hetween the joints by 

 the projection of the angles, whence the filament has a pinnatifid appearance. 



The transverse view is triangular ; the angles are blunt and the sides 

 slightly concave. The endochrome is in three portions, placed in the angles 

 and connected together at the centre ; but this arrangement of the endo- 

 chrome is seen only when the joints separate spontaneously. The rays are 

 usually bipartite. When a joint is separated by force under the microscope, a 

 cloud of minute granules is poured out and for an instant obscures the view. 



Mr. Borrer has kindly presented me with a portion of a specimen of the 

 plant here described, which was given him by Mr. Dawson Turner as the 

 Conferva dissiliens of Dillwyn. 



I have gathered at Dolgelley some fragments of this plant which had the 

 endochrome condensed into a sporangium-like body in the centre of each joint. 

 As in every other species of this family in which the reproductive body has 

 been detected, it is the result of the coupling of the cells, I think it best 

 merely to direct attention to the fact I have mentioned, leaving its nature to 

 be determined by future observation. 



Length of joint from -o^q-q to y-gVe" ^^ ^^^ inch ; breadth of filament -^^. 



Tab. IV. a. portion of a mature filament ; b. portion of a filament with the 

 joints dividing; c, d, e. transverse views ; f. sporangia? 



2. D. quadrangulatum (Ralfs) ; filaments quadrangular, varying in 

 breadth from the twisting of the filament and having two longi- 

 tudinal waved lines; the end view quadrangular with the endo- 

 chrome four- rayed. 



Desinidium, quadrangulatum, Ralfs, iii Annals of Nat. Hist. v. 15. p. 405. 



t. 12. f. 9. (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 163. 

 Desmidium quadrangtdare, Kiitz. Phy. Germ. p. 141 (1845). 



Hab. In a boggy pool at Bologas near Penzance ; Dolgelley, J. R. Amble- 

 side, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant. 



The Harz, Germany, Kutzing. 



Mr. Berkeley and Mr. Borrer regard this plant as a variety of D. Swartzii, 

 and certainly all the more obvious distinctive marks depend upon the filament 

 being quadrangular in one case and triangular in the other*. As I have 

 gathered it for two succeeding years quite unmixed with Desmidium Swartzii, 

 and as Mr. Berkeley well observes (in a letter), that " whether considered as a 

 species or variety, it is a remarkable plant and well-deservuig of notice," I 

 have preferred to describe it as distinct, although I do not consider the point 

 free from doubt. As there are three sides in one plant and four in the other, 

 whilst the sides in both are equal, the filament of D. quadrangidatum is 

 stouter ; for the same reason, instead of one dark longitudinal line it has two 



* " Est-il reellement plus distinct du D. Swartzii que les Staurastr. a quatre 

 ravons des Staur. a trois ravons?" — Bn'bisson in lit. 



