BRITISH DESMIDIE.E. 125 



Length of frond -^\-^ of an inch ; breadth -^^ ; breadth at constriction 



2 TTB- ; le»gth of spine ^rhr- 



Tab. XXXIV. fig. 12. a. front view ; b. end view. 



** Frond smooth ; angles in end view broadly rounded. 



7. >S. muticum (Breb.) ; segments smooth, elliptic, end view showing 

 slightly concave sides and 3 — 5 rounded angles. 



Binatella muticmn, Brebisson, AJg. Fal. p. b7 • t. 8 (1835). 

 Staurastrum trilohum, Meneghiui, Conspect. Alg. Eug. p. 18 (1837). 

 Staurastrum muticum, Breb. in Menegh. Synop. Desmid. in Linncea 1840 ; in 

 lit. cum icone. 



Dolgclley and Penzance, J. R. Ambleside, Mr. Sidebotham. 



Falaise, Brcbisson. Italy, Meneghini. 



The frond, generally smaller than that of Staurastrum orbiculare, is quite 

 smooth and has a mucous covering, which is sometimes distinct, but often it 

 can only be ascertained by the appearance of a clear border round the frond 

 which prevents the contact of other substances ; segments eUiptic. The end 

 view shows three or four angles, sometimes five, according to Meneghini ; the 

 sides are slightly concave and the angles broadly rounded. 



Staurastrum muticum differs from S. orbiculare by its elliptic segments 



and mucous covering. 



Length of frond -^\^ of an inch ; breadth ^-|^ ; breadth at constriction 

 1 



2 500* 



Tab. XXI. fig. 4. a, b. front view ; c. end view of three-rayed state ; 

 d. end view of four-rayed variety. 



Tab. XXXIV. fig. 13. Sporangium, from a drawing by M. de Brcbisson. 



8. S. orbiculare (Ehr.) ; segments smooth, semiorbicular ; end view 

 bluntly triangular. 



Besmidium orbiculare, Ehr. Abh. der Berl. Ak. 1832, p. 292 ; Infus. p. 141. 



t. 10. f. 9. 

 Staurastrum orbiculare, Ralfs, in Annals of Nat. Hist. v. 15. p. 152. t. 10. 



f. 4. (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 138. t. 13. 



Jeimer, Fl. of Tunbridge Wells, p. 96. Brebisson, in lit. cum icone. 

 Phycastrum orbiculare, Kiitzing, Phy. Germ. p. 137 (1845). 

 Goniocystis (Trigonocystis) orbicularis, Hassall, Brit. Freshwater Algce, 



p. .349 (1845). 



Dolgelley and Penzance, J. R. Sussex ; Kent ; and Weston Bogs near 

 Southampton, Mr. Jenner. Ben Muich Dhu (alt. 3480 feet), Aberdeenshire, 

 Dr. Dickie. Aberdeenshire and Banffshire, Mr. P. Grant. Ambleside, 

 Westmoreland, Mr. Sidebotham. 



Germany, Ehretiberg and Kiitzing. Falaise, Brebisson. West Point, New 

 York, Bailey. 



Frond smooth, deeply constricted at the middle ; the segments are gene^ 

 rally in close approximation for their entire breadth, hence the frond is sub- 

 orbicular. The end view is triangular, with sides either straight or slightly 

 concave and rounded angles. 



