STAURASTRUM. 1 1 



cit.) records this variety for Woodbury Common, E. Devon, 

 which is the first British locality for it. Exactly what Wolle 

 intended us to understand by his variety convergens is difficult 

 to decide. His figures are very bad, and some of them bear a 

 strong resemblance to St. glabrum (Ehr.) Kalfs, or to ArtJiro- 

 desmus convergent Ehr. The writer is of the opinion that Wolle's 

 description and figures are wholly inadequate as the basis of a 

 valid variety, and believes that specimens recorded under this 

 name have in all probability been either forms of Staurastrum 

 glabrum or simply St. dejection with slightly convergent spines. 



46. Staurastrum mucronatum Ralfs. 

 (PL CXXX, figs. 10-12.) 



Staurastrum mucronatum Ralfs in Ann. Mag. Xat. Hist. 1845, p. 152, t. 10, 

 f. 5, 6 (ex parte) ; Breb. Liste Desm. 1856, p. 142 ; Xordst. Desm. 

 Spetsb. 1872, p. 38 ; Gay, Monogr. loc. Conj. 1884, p. 67 ; Roy & Biss. 

 Scott. Desm. 1894, p. 22; West & G. S. West, Alga-fl. Yorks. 1902, 

 p. 96 ; Ale. X. Ireland, 1902, p. 44, t. 2, f. 31 ; Borge, Botan. Xotis. 1913, 

 p. 28. 



Goniocystis (Trigonocystis) mucronata Hass. Brit. Freshw. Alg. 1845, p. 350, 

 t. 84, f.8 (ex parte). 



Staurastrum dejectum ft Ralfs, Brit. Desm. 1848, p. 121, t. 20, f. 5 (ex parte). 



Phycastrum (Amblyactinium) mucronatum Xiig. Gatt. einz. Alg. 1849, p. 125. 



Staurastrum dejectum forma Reinsch, Contrib. Alg. et Fung. 1875, p. 90, 

 t. 13, f. 7. 



St. dejectum var. mucronatum Kirchn. Alg. Schles. 1878, p. 169 ; Wolle, 

 Desm. U. S. 1884, p. 121, t. 40, f. 8 ; Cooke, Brit. Desm. 1887, p. 139 

 t. 55, f. 7 ; De Toni, Syll. Alg. 1889, p. 1137 ; Gutw. Xonn. Alg. Xov. 

 1896, p. 27, t. 7, f. 69;' Comere, Desm. de France, 1901, p. 161, t. 12, 

 f. 28 ; Teodoresco, Mater, flor. alg. Rouman. 1907, p. 183. 



Cells small, about as long as broad, deeply constricted, 

 sinus open and acute-angled ; semicells elliptic, dorsal 

 margin more convex than in St. dejectum, ventral margin 

 more convex than the dorsal ; angular spines rather 

 short, projecting horizontally, rarely converging. Ver- 

 tical view usually triangular, lateral margins concave, 

 angles very turgid, ending in a short stout spine. Criloro- 

 plast axile with a central pyrenoid, and a pair of lobes 

 stretching into each angle. 



Zygospore spherical, furnished with numerous conical 

 spines. 



Length 22-26 y. ; breadth, without spines, 18-25 a. ; 

 length of spines 3-3*5 y. ; breadth of isthmus 6 '7-7 [j. ; 



