ADDENDA. 205 



Desmid only known from Gronnedal in South Greenland. From 

 this, Arctic Desmid E. laticolle differs in the form of the front 

 view, having a closed and linear sinus, and lateral lobes of quite 

 a different shape. The general outline of the vertical view is 

 the same as in E. Berlini, but in the latter species the polar 

 lobe is described (and also figured) by Boldt as " broadly ellip- 

 tical" when seen in the end view, whereas that of E. laticolle is 

 rectangular with retuse sides and rounded angles. 



Euastrum affine Ealfs (vol. ii, p. 17). 

 Forma scrobiculata Xordst. 



il fijjine f. s<-r<il,i<-nlit<i Nnnl.-t. Xorges Desin. 1ST:>, p. 8 : Harris, in 

 Joum. Quek. Micr. Club, 11(17, p. LV><>. 



The chief distinction of this form is the presence of a con- 

 spicuous ocellation in the middle of the semicell, which takes 

 the place of the two upper tumours. 



ENGLAND.- -Devonshire 



Euastrum montanum West (vol. ii, p. 58). 

 (PL CLXVII, fig. 5.) 



The zygospore of Euastrum montanum has been figured by 

 Liitkemuller (<Zur K. d. Desm. Bohm.' 1910, p. 483). It is 

 spherical with numerous tubercles, each tubercle ending in a 

 simple hooked spine. Diam. zygosp. without spines, 29 /< ; 

 including spines 



Euastrum insulare (Wittr.) Roy (vol. ii, p. 68). 



Var. parvum West. 



Eu. insulare var. par nun West, Clare Isl. Alg. 1912, p. 15. 



Cells similar to the typical form, but smaller, and 

 relatively shorter, margins of lateral lobes less retuse. 



Length 12-5-17 \L ; breadth 10-13 \L. 



IRELAND.- -Xear Dugort, Achill Isle, and near Castle- 

 bar, Mayo ! 



