142 BRITISH DESMIDIEJE. 



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



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



Jenner, FI. of Tunhridge Wells, p. 194. 

 Goniocystis (Trigonocystisi) 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 tban long, elliptic 

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

 pering into a short process, which is termmated 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 mimite subulate spines. In both Adews the fronds show nu- 

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



I formerly considered this plant to be the Staurasti'iim aculeatum, and I 

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

 diflFers except in its processes, which are always straight. 



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

 constriction 3-j^. 



Tab. XXIII. fig. 3. a, b, c. front \aews ; 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. 



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



Pritchard, Infus. p. 184. 

 Staurastrum aculeatum, Meneghini, Synop. Desmid. in Linncea 1840, p. 226. 

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



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

 Dolgelley, J. R. Ambleside, 3Ir. Sidebotham. 



Germany, Ehrenberg. Falaise, Brebisson. 



Frond about as large as that of Staurastrum. controversum, deeply con- 

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

 each side ; segments broader than long, somewhat fusiforai, 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 -g-i^ ; breadth at constriction 

 1 



1 6 6 6- 



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

 view of four-raved variety. 



