56 BRITISH DESMIDIACE^. 



32. Euastrum denticulatum (Kirclm.) Gay. 

 (PI. XXXIX, figs. 1-4.) 



Euastrum binale var. /3 Balfs, Brit. Desiu. 1848, t. 14, f. 8 a and/. 



E. binale b. denticulatum Kirclm. Alg. Schles. 1878, p. 159 ; Cooke, Brit. 



Desm. 1886, p. 76, t. 35, f. 7 ; Hanso-. Prodr. Algenfl. Bohiu. 1888, 



p. 252. 



E. amcenum Gay, Monogr. loc. Conj. 1884, p. 53, t. 1, f. 7. 

 E. denticulatum (Kirclm.) Gay, Note Conj. du midi de France, 1884, 



p. 335; West, Alg. W. Ireland, 1892, p. 140; Alg. Eng. Lake Distr. 



1892, p. 723 ; Roy & Biss. Scott. Desm. 1893, p. 176 ; West & G. S. 



West, Alg. Madag. 1895, p. 53, t. 9, f . 15, 16 ; Nordst. Index Desm. 



1896, p. 100 ; West & G. S. West, Welw. Afric. Freshw. Alg. 1897, p. 84 ; 



Alg. S. England, 1897, p. 484; Alga-fl. Yorks. 1900, p. 64; Chlorophy. 



Koh Chang, 1901, p. 85 ; Alg. N. Ireland, 1902, p. 29 ; Scott. Freshw. 



Plankton, I, 1903, p. 525. 

 Helierella Kirchneri Kuntze, Eevis. gen. plant. 1891, p. 898. 



Cells very small but rather variable in size, about 

 1J times as long as broad, very deeply constricted, 

 sinus narrowly linear with a dilated extremity ; semi- 

 cells subquadrate or subpyramidate, almost trapezoid, 

 basal angles rounded or subrectangular, furnished with 

 a number of granules or denticulations, upper part of 

 lateral margins concave, apical part of semicell pro- 

 tracted, broadly rectangular, upper angles furnished 

 with an acute granule or short spine, apex truncate 

 with a slight median notch (sometimes only retuse- 

 emarginate) ; semicells with a granulated central pro- 

 tuberance, and a number of granules or denticulations 

 within the basal angles and the apex. Side view of 

 semicell ovate, with an acute apex, and an emarginate 

 or granulated protuberance at each side near the base. 

 Vertical view elliptic, poles acute, with an emarginate 

 or granulate protuberance at the middle on each side. 



Zygospore unknown. 



Length 13-26 JJL; breadth 11-5-21 //,; breadth of 

 isthmus 3'5-6*5 JJL; thickness 7*5-14 p.. 



ENGLAND. Cumberland! Westmoreland! W., ]N T ., 

 and E. Yorks ! Lancashire ! Surrey ! Kent ! Hants ! 

 (Roy). Devon! Cornwall! 



WALES. Frequent through Carnarvonshire (up to 

 2,200 ft. on Glyder Each) ! Dolgelly, Merioneth ! 



SCOTLAND. Generally distributed! (Roy $ liissett). 

 General in the Outer Hebrides ! Orkneys ! Shetland s ! 



