BRITISH DESMIDIACE.E. 



f f Cell-wall rough with tiny granules. 



67. St. denticidatum. 



68. St. Avicula. 



69. St. subcruciatum. 

 60. St. cornutum. 



42. Staurastrum glabrum (Ehr.) Kalfs. 

 (PI. CXXIX, figs. 2-5.) 



Desmidium glabrum Ehr. Meteorpap. 1838, pp. 51 and 56, t. 1, f. 13 (in part). 

 Phycastrum glabrum Kiitz. Phyc. Germ. 1845, p. 137 ; Spec. Alg. 1849, 



p. 179. 

 Staurastrum glabrum Ralfs, Brit. Desm. 1848, p. 217 ; Arch, in Pritch. Inf. 



1861, p. 738 ; Cooke, Brit. Desm. 1887, p. 143, t. 50, f . 4 ; De Toni, Syll. 



Alg. 1889, p. 1145 ; Roy, Freshw. Alg. Enbridge Lake and Vicin. 1890, 



p. 337 ; Roy & Biss. Scott. Desm. 1893, p. 20 ; West & G. S. West, Some 



N. Amer. Desm. 1896, p. 255, t. 16, f. 8 (var.) ; Alg. N. Ireland, 1902, 



p. 44 ; Borge, Botan. Notiser, 1913, p. 28. 



Phycastrum (Stenactinium) glabrum Nag. Gatt. einz. Alg. 1849, p. 128. 

 Staurastrum dejectum ft Debaryanum forma Borge, Sverig. Chlorophyc. II, 



1895, p. 23, t. 1, f. 14. 



Cells very small, about as long as broad, not in- 

 cluding trie spines, or sometimes a little broader than 

 long, deeply constricted, sinus widely open and almost 

 rectangular ; semicells in front view cuneate, sides 

 straight or very slightly convex, apex straight or slightly 

 concave, with a long, strongly inflexed spine at each 

 angle. Vertical view usually triangular, sides slightly 

 concave, angles ending in a sharp spine. Chloroplasts 

 axile, one in each semicell, with a central pyrenoid, 

 and a pair of lobes extending into each angle. 



Zygospore "globular, spines numerous, simple, subu- 

 late, base broad : (Roy). 



Length 16-25^ ; breadth, without spines, 15-30(JL ; 

 length of spines 7-10(ji; breadth of isthmus 5-7 JJL ; 

 diam. zygosp., without spines, 25' 6^ ; length of spines 

 14*4 [JL. 



ENGLAND. Cam Fell and bog near Clapham, W. 

 Yorks ! Mickle Fell, N. Yorks ! Bisley Common, 

 Surrey ! Enbridge Lake, Hants (Roy}. Devon ! 

 (Harris). Cornwall (Marquand). 



WALES. Moel Siabod, Llyn Bochlwyd, Glyder Fach 



