48 BRITISH DESMIDIACE^. 



30. Euastrum elegans (Breb.) Kiitz. 

 (PL XXXVIII, figs. 16-21.) 



Heterocarpella elegans Breb. in Coeval, microscop. et usage, Paris, 1839, 

 p. 72 (name only). 



Cosmarium elegans Breb. in Menegh. Synops. Desm. 1840, p. 222. 



Euastrum elegans (Breb.) Kiitz. Phycol. germ. 1845, p. 135 ; Ealfs, Brit. 

 Desm. 1848, p. 89, t. 14, f . 7 6, c, and d , Arch, in Pritch. Infus. 1861, 

 p. 730; Rabenh. Flor. Europ. Algar III, 1868, p. 185; Cooke Brit, 

 Desm. 1886, p. 74, t. 35, f . 3 ; De Toni, Syll. Alg. 1889, p. 1101 ; West, 

 Alg. W. Ireland, 1892, p. 139 ; Roy. & Biss. Scott. Desm. 1893, p. 176 ; 

 Nordst. Index Desm. 1896, p. 116 ; West & G. S. West, Alg. S. England, 

 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 63 ; Alg. N. Ireland, 1902, p. 28 ; 

 Scott. Freshw. Plankton, I, 1903, p. 525. 



E. elegans from declivis Reinsch, Spec. Gen. Alg. 1867, p. 124, t. 20, f. 

 D III 1-3. 



Didymidium (Euastrum) elegans Reinsch, Algenfl. Frank. 1867, p. 136. 



Euastrum elegans a. typicum Kirchn. Alg. Schles. 1878, p. 159. 



E. declive Roy in Bates' Flora Leicestershire, 1886, p. 35. 



E. elegans var. Lundellii Istvanffi. Diag. praev. Alg. nov. Hungar. 1887, 

 p. 236 (Ralfs I.e. fig. 7 5 and c). 



Helierella elegans Ktintze, Revis. gen. plant. 1891, p. 898. 



Cells very small, about 1^ times longer than broad, 

 deeply constricted, sinus narrowly linear; semicells 

 ovate-pyramidate, basal angles subrectangular, retuse- 

 emarginate, above with the sides concave, superior 

 angles apiculate, apex strongly convex (or broadly 

 rounded) with a deep and narrow median incision; 

 semicells with a triverrucose or a granulate protu- 

 berance in the centre above the isthmus, the rest of 

 the cell-wall generally smooth. Side view of semicell 

 ovate, with a truncately-rounded apex, and an emar- 

 ginate protuberance on each side above the base. 

 Vertical view elliptic, with acute poles, and an emar- 

 ginate protuberance in the middle on each side. 



Zygospore globose, furnished with simple acute 

 spines. 



Length 29-36'5 p. ; breadth 19-22 p,; breadth of 

 isthmus 5 '8-7 ^ ; thickness 10-14*5 ^ ; diam. of zygosp. 

 without spines 20-29 /i; length of spines 7'5-9'5 /x. 



ENGLAND. Cumberland ! Westmoreland ! (Ralfs). 

 W., N., and E. Yorks! Lancashire! Cheshire (Ralfs}. 

 Leicestershire (Roy). Essex ! Warwick (Wills). 

 Gloucestershire (Ralfs). Surrey! (Ralfs). Sussex 



