126 BRITISH DESMIDIF.iE, 



Staurastruin orhiculure may be recognized by its smootb frond, angles 

 broadly rounded and destitute of processes, and its orbicular form in a front 

 view. 



Sporangia, gathered at Dolgelley and Penzance, are orbicular, •with subulate 

 spines. The conjugating fronds are smaller than those in the ordinary state. 



Length of frond ^^^zi ^^ ^"^ i\ic\i ; breadth ytW '■> breadth at constriction 

 g-gL- ; diameter of sporangium ^^ ; length of spine -^-f-^-^. 



Tab. XXI. fig. 5. a, c, d, h. front view; b,f, i. end view; e. transverse 

 view ; g. sporangium. 



9. S. tumidum (Breb.) ; segments smooth, elliptic or suborbicular ; 

 end view bluntly triangular, each angle terminated by a nipple-like 

 projection. 



Binatella tumida, Brebisson, Alg. Fal. p. 66 (1835). 



Staurastrum orSiCM/are, Meneghini, Synop. Desmid. in Lmncea 1840, p. 225. 



Staurastrum tumidum, Brebisson, in lit. cum icone (1846). 



Piltdowu Common, Sussex, Mr. Jeriner. Dolgelley and Penzance, J. R. 



Falaise, Brebisson. 



Frond large and distinctly \-isible to the naked eye, smooth, deeply con- 

 stricted at the middle, having a distinct gelatinous covering, which is often 

 marked with close radiating striae ; segments elliptic or suborbicular. The 

 end view is triangular or quadrangular, the sides are convex, the angles 

 rounded, and each terminated by a nipple-like process ; some of these pro- 

 jections are visible in the front view. In both views the margin of the frond 

 appears striated. The empty frond is minutely punctate. 



Length of frond -^^-^ of an inch ; breadth -^-^ ; breadth at constriction 4-g-o. 



Tab. XXI. fig. 6. a. front \'iew ; b. end view of triangular form ; c. end 

 view of quadrangular variety magnified only 200 times ; d. transverse view. 



*** Frond with simple spines, hairs, or (rarely) acute granules ; 

 angles, in end view, broadly rounded and entire. 



10. S.muricatum (Breb.) ; segments semiorbicular, rough with conic 

 granules; end view triangular, with convex sides and broadly 

 rounded angles. 



Binatella muricata, Brebisson, Alg. Fal. p. dQ (1835). 



Besmidium apicidosum, Ehrenberg, Infus. p. 142 (1838). Pritchard, Infus. 



p. 184. 

 Staurastrum muricatum, BreTjisson, INIeneghini, Synop. Desmid. in Linncea 



1840, p. 226. 

 Xanthidivm deltoideum, Corda, Obscrv. Microscojriqiies sur les Animalcules 



de Carlsbad, p. 21). t. 5. f. 38, 39 (1840). 

 Staurastrum muricatum ft, Ralfs, Annals of Nat. Hist. v. 15. p. 154. t. II. 



f. 1. d, e. (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 141. t. 14. 

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



