ST AURA STRUM. 155 



20. Staurastrum orbiculare Ralfs. 

 (PL CXXIV, figs. 10, 11.) 



? Desmidium orbiculare Ehrenb., 1834; Infus. 1838, p. 141, t. 10, f. ix. 

 Staifi'asti-c.m orbiculare f? Menegh. Synops. Desni. 1840, p. 225] ; Ralfs in 



Ann. Mag. Nat. Hist, xv, 1845, p. 152, t. 10, f. 4; Ralfs, Brit. Desm. 



184s, p. 125, t. 21, f. 5 h and i ? [not figs. 5 a-g~] ; Arch, in Pritcli. 



Infus. 1861, p. 740 ; Rabeiih. Flor. Europ. Alg. Ill, 1868, p. 200 ; Lund. 



Desni. Suec. 1871, p. 56 ; Delp. Desm. subalp. 1877, p. 37, t. 10, f. 11 



and 12 fnot f. 5-10] ; ? Wolle, Desm. U. S. 1SS4, p. 120, t. 39, f. 9, 10; 



? De Toni, Syll. Alg. 1889, p. 1180 ; Nordst. in Wittr., Nordst, & Lagerh. 



Al. Exsic. 1903, no. 1472 ; fasc. 35, 1903, p. 9 "in. part]. 

 Goniocystis (Trigonocystis) orbictdaris Hass. Brit. Fresh w. Al<. 1845, 



p. 349, t. 84, f. 7. 



Ph yeast rum orbiculare Kiitz. Phyc. germ. 1845, p. 137. 

 Didymidium (Staurastrum) orbiculare Reinsch, Alg-eiin. Frank. 1867, 



p. 152 ~in part]. 

 ? Staurastrum orbiculare forma punctnta Gutw. "\Vahr. d. Prioritiit, 1890, 



p. 71 ; Flor. Glon. Okolic Lwowa, 1891, p. 65, t. 3, f. 10. 

 St. Farqxlinrsonii, Roy & Biss. Scott. Desm. 1893, p. 237, t. 4, f. 3. 

 St. hibernicum West var. Farquharsonii (Roy & Biss.) W. & G. S. West, 



Notes Alg. II, 1900, p. 296, t. 412, f. 21. 



Cells of medium size, a little longer than broad, 

 almost circular in general outline, very deeply con- 

 stricted, sinus narrowly linear with a slightly dilated 

 extremity; semicells subsemicircular, apex a little 

 depressed but scarcely truncate, basal angles some- 

 what rounded. Vertical view triangular, sides slightly 

 concave, angles broadly rounded. Cell-wall punctate. 



Zygospore unknown. 



Length 54'4 56 p. ; breadth 46'5-49/x; breadth of 

 isthmus 1 1-12*5 p.. 



Ex< ; LAND. Hampsf ell, Lancashire ! Cornwall (Ralfs) . 



SCOTLAND - -Alford, Aberdeen (Roy Bissett). 



<ieoiji\ Distribute on. --Germany. Austria (?). Sweden. 

 Finland. Italy. 



The Desmid described above must be taken as the type 

 form of St. orbiculare, as it is identical with the Staurastrum 

 described and fio-ured by Ralfs in 1845 under that name. 



t/ 



Ralfs identified his plant with " Desmidimn orbiculare 

 Ehrenb./' but as that is open to some doubt,, we regard Ralfs 

 as the author of the species. 



In 1848,, although Ralfs did not alter his description, he 

 included other forms among- his figures. Thus, of the figures 

 in his ' British Desmids/ t. 21, only figs. 5 //. and i represent 

 typical St. orbiculare, and even these figures ar p not good. 



