STAURASTRUM. 81 



Cells not so angular as in the type, sinus a little more 

 open, and distinctly swollen at the apex ; a few of the 

 spines longer than in the type, the remaining ones 

 normal. 



Length 32 pi; breadth 30 '5 fi ; breadth of isthmus 

 97 (JL. 



IRELAND. SHeve Donard, Co. Down (abundant 

 amongst Sphagnum) \ 



100. Staura strum scabrum Breb. 

 (PL CXL, figs. 1, 2.) 



St. scabrum Breb in Ralfs, Brit, Desm. 1848, p. 214, t. 35, f. 20 ; Arch, in 

 Pritch. Infus. 1801, p. 740; Rabenh. Flor. Europ. Alg. 1868, p. 217; 

 Lund. Desm. Suec. 1871, p. 65 ; Wolle, Desm. U. S. 1884, p. 130, t. 41, 

 f. 29, 30 ; Boldt, Desm. Gronland, 1888, p. 39, t. 2, f. 50 ; De Toni, 

 Syll. Alg. 1889, p. 1170; West, Alg. X. Wales, 1890, p. 18; Ltitkem. 

 Desm. Attersees, 1893, p. 564 ; Roy & Biss. Scott. Desm. 1893, p. 25 ; 

 Borg. in Wittr. & Nordst. Alg. exs. no. 1114, 1893, p. 11; Schmidle, 

 Beitr. Alp. Alir. 1896. p. 32 ; Comere, Desm. de France, 1901, p. 170, 

 t. 13, f. 6 ; West & G. 8. West, Alg. N. Ireland, 1902, p. 51, t. 2, f. 36 ; 

 Brit. Freshw. Phytoplankton, 1909, p. 203. 



Cells small, a little longer than broad, deeply con- 

 stricted, sinus open and acute ; semicells elliptic- 

 fusiform or subtrapeziform, dorsal margin mor econvex 

 than the ventral, peripheral margin granulate, lateral 

 angles subtruncate with about 3 acute granules at each ; 

 cell- wall granulate, granules arranged in 8 longitudinal 

 rows down the face of the semicell, those near the angles 

 consisting of simple granules, but in the 4 median series 

 the granules scattered in groups. Vertical view trian- 

 gular, angles rounded, sides very slightly concave, mar- 

 gins denticulate, granules in the median part of the 

 lateral margins often emarginate, and with about 2 series 

 of emarginate granules just within the margin. ^ Chloro- 

 plast axile, with a central pyrenoid in each semicell and 

 a pair of lobes extending into each angle. 



Zygospore globular, sometimes slightly oblong, with 

 short stout spines 3- or 4-fid at the apex, about 10-13 

 visible round the margin (Roy & Biss.). 



Length 35-36 u. ; breadth 32-38 (i ; breadth of isth- 



t> - r- a 



VOL. V. 



