PEXIUM. 93 



s quantity in small pools in the best bogs of the 

 country. The widest part of the cell is ahvays in the middle, 

 and the apices are always flattened. Most specimens have 

 two chloroplasts situated close together in the middle region 

 of the cell, and each furnished with a pyrenoid, but others 

 have only one median chloroplast with one pyrenoid. The 

 frequent reduction of the longitudinal ridges to two is also 

 noteworthy. This same reduction of the chloroplasts we have 

 observed in Cosmocladium constrictum Arch. 



P. xnljfil' can be compared with Dysphinctii.im sparsi- 

 /noictatuin Schmidle, from the nnconstricted form of which it 

 differs in the shape of its cells, its much more delicate pmictu- 

 lations, and its circular vertical view. 



20. Penium adelochondrum Elfv. 

 (PI. VIII, figs. 30, 31.) 



Penium adelochondrum Elfv. Auteck Finska. Desru. 1881, p. 17, t. 1, f. 13 ; 

 West, Alg. W. Ireland, 1892, p. 128 ; Eoy & Biss. Scott. Desni. 1S94, 

 p. 251 ; Nordst. Index Desm. 1896, p. 40. 



Cells small, 2|-2f times longer than their diameter, 

 subcylindrical, gradually narrowed towards each pole, 

 with a slight median constriction, apices broadly 

 truncate ; cell-wall somewhat sparsely scrobiculate. 



Zygospore unknown. 



Length 40-4(3 n ; breadth 1(3-20 f i ; breadth of apices 



10-12-5 ju. 



SCOTLAND. Poolewe, Ross ; Grlen Sligachaii in Skye, 

 Inverness; Grlen Cattie, Aberdeen (Roy $' IJissctt). 

 Rhiconich, Sutherland ! 



IRELAND. Cromagloim and Tore Mt., Kerry I 

 Geogr. Distribution. Germany. Austria. Finland. 

 West Africa. 



21. Penium lagenarioides Roy. 



(PI. IX, fig. 12.) 



Penium lagenarioides Eoy, in Biss. Desm. Windermere, 1884, p. 197, t. 5, 

 f . 6 ; Cooke, Brit. Desm. 1886, p. 45 ; Eoy & Biss. Scott. Desm. 1894, p. 

 252 ; Nordst. Index Desni. 1896, p. 154. 



Cells large, ellipsoid, about twice longer than their 

 diameter, with a very slight median constriction, 

 semicells gradually attenuated towards the apices, 



