244 BRITISH DESM I PL AC K.. 



208. Cosmarium pycnochondrum Nordst. 

 (PI. LXXXVIII, fig. 7.) 



Cosmarium pycnochondrum Xorclst. Desm. Arctose, 1873, p. 23, t. 6, f. 14 ; 

 ? Wolle, Desm. U. S. 1884, p. 89, t. 19, f. 10-11 ; Boldt, Desm. Gron- 

 land, 1888, p. 21 ; De Toiii, Syll. Alg. 1889, p. 1021 ; Eoy & Biss. Scott. 

 Desm. 1894, p. 173 ; Xordst. Index Desm. 1896, p. 214. 



Ursinella pycnochondra Kuntze, Eevis. gen. plant. 1891, p. 925: 



Cells of medium size, about 14- times as long as 

 broad, subhexao-onal in outline, sinus very narrowly 



rr> / ./ 



linear ; semicells trapeziform, sensibly narrowed from 

 a broad straight base to a truncate apex, basal angles 

 obtuse, sides slightly convex and 5-6-crenate, apical 

 angles rounded, apex 4-crenate (including the apical 

 angles), crenations 2-3-granulate, within the margin 

 with numerous minute granules arranged in con- 

 spicuous radiating and rather indistinct concentric 

 series, grouped in twos or threes within the crena- 

 tions ; with a granulate area across the basal part of 

 the semicells above the isthmus, eranules arranged in 



' ~ O 



912 vertical (slightly divergent) series, and with a 

 smooth area immediatelv above these granules. Side 



. o 



view of semicell rectangular, superior angles rounded 

 and minutely granulate, at the base on each side with 



/ o f 



a slight granulate inflation. Vertical view elliptic- 

 oblong, with the poles and the median portion of the 

 sides minutely granulate. Chloroplasts axile, with 

 two (?) pyrenoids. 



Zygospore unknown. 



Length 58-64 ^ ; breadth 48-53 JJL ; breadth of 

 isthmus 20*4-24 /x; breadth of apex 21'0-27/ix; thick- 

 ness 30-33 //,. 



SCOTLAND.- -Mount Keen and Colonel's Bed (Brae- 

 mar), Aberdeen; Den of Garrol, Kincardine; Clova 

 Tableland, Forfar (Eoy $ Bissett). 



Geoc/r. Di*tril>ntion. Greenland. Spitzbergen. 

 United States (?). 



This alpine and arctic Desmicl differs from C. speciosnm 

 in the much greater width of the cells as compared with their 

 length, and in the denser nature of its granulation. As in 



