30 BRITISH DESMIDIACE.E. 



Geofjr. Distribution. India. Burmali. Singapore 

 (var.). Sumatra. Madagascar (var.). 



All the examples of this species which we have seen 

 possessed a smooth cell-wall. Turner also found that Indian 

 specimens had a smooth cell-wall; his measurements are : 

 length 58-65 /m ; breadth 37-44 /n ; breadth of isthmus 1 6-17 /m. 

 Joshua describes the cell-wall as of " a faint flesh-colour, 

 sometimes indistinctly granulated." His original measure- 

 ments are : length 50-80 in ; breadth 30-35 /.t ; breadth of 

 isthmus 9-15 /u. 



It is distinguished from E. ansatum by its relatively-greater 

 breadth and by the broadly-rounded basal part of the semi- 

 cells. There is also an absence of the longitudinal lines of 

 punctulations which are such a characteristic feature of E. 

 ansatum. 



16. Euastrum pingue Elfv. 

 (PI. XXXVII, fig. 1.) 



Euastrum sp. Arch, iu Quart. Journ. Micr. Sci. 1871, p. 93 (according to 



Roy). 

 Euastrum pingue Elfv. Anteck. Finska Desm. 1881, p. 7, t. 1, f . 3 ; Wolle, 



Desm. U.S. 1884, p. 105, t. 27, f. 1-3 ; De Toni, Syll. Alg. 1889, p. 1098 ; 



Roy & Biss. Scott. Desm. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 201. 

 E. Armstrongianum Arch, in Ann. Mag. Nat. Hist. 1883, p. 213. 

 Helierella pinguis Kuntze, Eevis. gen. plant. 1891, p. 899. 



Cells small, almost H times longer than broad, very 

 deeply constricted, sinus slightly open for more than 

 half its length, then narrowed; semicells rounded- 

 pyramidate, basal angles broadly rounded (faintly 

 subrectangular) upper portions of lateral margins 

 retuse ; apex convexo-truncate, with a widely-open, 

 shallow, median notch. Cell- wall scrobiculate ; scrobi- 

 culations larger in the centre of the semicells, at the 

 apex, and at the basal angles, causing these parts of 

 the cell-wall to appear rough on the surface ; with a 

 larger, somewhat irregular scrobiculation in an excentric 

 position near the centre of the semicells. Semicells 

 with a small papilla at each basal angle at the beginning 

 of the sinus ; also with a large granule in the middle 

 and close to the isthmus. Side view of semicell ovate, 

 apex rounded, sides slightly retuse just below the 

 apex ; with a granule at each side at the base, close to 



