MICEASTEKIAS. 83 



Als. W. Ireland, 1892, p. 135 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Eoy 

 and Biss. Scott. Desm. 1893, p. 175 ; Nordst. Index Desm. 1896, p. 260 ; 

 West & G. S. West, Alg. S. England, 1897, p. 484 ; G-. S. West, Varia- 

 tion Desm. 1899, p. 383, t. 9, f. 9-16 ; West & G. S. West, Alga-fl. 

 Yorks, 1900, p. 65 ; Alg. N. Ireland, 1902, p. 30. 



Micmsterias quadragies-cuspidata (Corda) Ealfs, Brit. Desm. 1848, p. 209. 



M. truncata var. quadrat a Buln. in Hedwigia, 1859, p. 21, t. 2, f. 2. 



Didymidium (Micrasterias) truncat utn f ornia b. dentatum Reinsch, Algenfl. 

 Frank, p. 144. 



Micmsterias truncata var. euastroides De Toni, Syll. Alg. 1889, p. 1115. 



M. truncata forma incisa De Toni, I.e. 



M. truncata var. quadragies-cuspidata De Toni, I.e. 



M. truncata var. tridentata Bennett, Freshw. Alg. Hamps. and Devon. 

 1890, p. 7 t, 1, f. 10. 



Helierella truncata Knntze, Eev. gen. plant. 1891, p. 897. 



Micrasterias truncata forma punctata West, Alg. W. Ireland, 1892, p. 135 ; 

 Alg. Eng. Lake Distr., 1892, p. 722. 



Cells small, generally a little longer than broad, 

 elliptical with widely truncate poles, deeply constricted, 

 sinus narrowly linear, often slightly open towards the 

 outside ; semicells scarcely 5-lobed, incisions below the 

 polar lobe moderately deep and generally somewhat 

 open (rarely narrowly linear), incisions between the 

 two lateral lobes slightly open and not so deep ; lateral 

 lobes somewhat variable, typically bilobulate with each 

 lobule emarginate ; polar lobe very widely cuneate 

 (sometimes almost fusiform), apex convex and usually 

 flattened or slightly retuse in the middle, lateral angles 

 acuminate or emarefinate. Side view of semicell 



O 



broadly ovate. Vertical view fusiform-elliptic, poles 

 acute. Cell- wall delicately or strongly punctate. 



Zygospore unknown. 



Length, .87-138 //,; breadth 78-129 p, ; breadth of 

 polar lobe 65-97 jn; breadth of isthmus, 18-27 ^ ; 

 thickness, 3652 p.. 



ENGLAND.- -Cumberland ! Westmoreland ! (Ealfs) . 

 W., K, and E. Yorks ! Lancashire ! Cheshire (Eoy). 

 Warwick! (Wills). Gloucester. Wilts! Surrey! 

 Sussex. Hants ! Devon ! Cornwall ! 



WALES. Common, especially abundant in the upland 

 bogs ! 



SCOTLAND. General and abundant ! (Eoy $' Bissetf). 



Outer Hebrides ! Orkneys ! Shetlands ! 



i/ 



IRELAND. General and abundant ! 



