142 BRITISH DESMIDIE^. 



Staurastrum aculeatum, Ralfs, Annals of Nat. Hist. v. 15. p. 156. t. 11. 



f. 4 (1845); Trans, of Bot. Soc. of Edinhurgh, v. 2. p. 142. t. 14. 



Jenuer, Fl. of Tunhridge Wells, p. 194. 

 Goniocystis {Trigo7iocystis1) aculeata, Hassall, Br. Freshwater Alg. p. 353 



(1845). 

 Dolgelley and Penzance, /. R. Reigate and Woking Common, Surrey ; 

 Cross-in-Hand, Piltdown Common, &c., Sussex, Mr. Jenner. Yate near 

 Bristol, Mr. Broome. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. 

 Grant. 



Falaise, Brebisson. 



Frond deeply constricted at the middle ; segments broader than long, elliptic 

 or fusiform, often irregular, but usually turgid on the inner side, laterally ta- 

 pering into a short process, which is terminated by minute spines and generally 

 curved or distorted. The end view is triangular or quadrangular, the angles 

 terminating in short, truncate, curved processes, which, as in the front view, 

 are tipped by miniite subulate spines. In both views the fronds show nu- 

 merous conspicuous spines which are either subulate or notched at the end. 



I formerly considered this plant to be the Staurastrum aculeatum, and I 

 still doubt whether it may not be a variety of that species, which scarcely 

 diflPers except in its processes, which are always straight. 



Length of frond -g^-^ of an inch ; breadth from -^\-^ to yig ; breadth at 

 constriction 3^^. 



Tab. XXIII. fig. 3. a, b, c. front views ; d. end view of three-rayed form ; 

 e. transverse view ; f. view of four-rayed variety ; g. transverse view ; h. spo- 

 rangium from a drawing by Brebisson. 



36. S. aculeatum (Ehr.) ; frond spinulose ; segments with a short 

 process on each side terminated by minute spines ; end view with 

 three to five straight rays terminated by spines. 



Desmidiitm aculeatum, Ehrenberg, Infus. p. 143. t. 10. f. 12 (1838). 



Pritchard, Infus. p. 184. 

 Staurastrtim aculeatum, Meneghini, Sy7iop. Desmid. in Linncea 1840, p. 226. 

 Phycastrum aculeatum, Kvltzing, Phycologia Germanica, p. 138 (1845). 



Weston Bogs near Southampton ; and near Pulborough, Sussex, Mr. Jenner. 

 Dolgelley, J. R. Ambleside, Mr. Sidebotham. 



Germany, Ehrenberg . Falaise, Brebisson. 



Frond about as large as that of Staurastrum conti'oversum, deeply con- 

 stricted at the middle, the constriction producing a broad triangular notch on 

 each side ; segments broader than long, somewhat fusiform, thickly spinulose, 

 the spines simple or notched at the apex. The segments taper on each side 

 into a short process tipped by three or four spines. The end view has from 

 three to five short straight rays terminated by spines. 



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

 1 



Tab. XXIII. fig. 2. a. front view; 6. end view of three-rayed form ; c. end 

 view of four-raved variety. 



