EUASTRUM. 13 



Euastrutn oblongiforme Cramer in Hechvigia, 1863, p. 64, t. 12, f. 3. 

 Didymidium (Euastrum) oblongum Reinsch, Algenfl. Frankeu, 1867, p. 136. 

 E. oblongum b. oblongiforme (Cram.) Rabenh. Flor. Europ. Algar. Ill, 



1868, p. 181; Racib! Nomi. Desm. Polon. 1885, p. 93; De Toni, Syll. 



Alg. 1889, p. 1087. 

 E. oblongum var. triyibbum Schaarschm. Magyar. Desm. 1882, p. 262, t. 1, 



f. 2. 

 E. oblongum forma? genuinx (1. typicum ; 2. subcylindricum 3. elongatum) 



Racib. Nonn. Desm. Polon. 1885, p. 93. 

 Helierella Pecten Kuntze, Revis. gen. plant. 1891, p. 897. 



Cells large, about twice as long as broad, in general 

 outline oblong-elliptic, deeply constricted, sinus nar- 

 rowly linear and slightly dilated at the apex; semicells 

 five-lobed, incisions between the lobes fairly deep and 

 generally slightly open (upper ones occasionally closed) ; 

 polar lobe widely cuneate, with rounded angles, apex 

 convex with a deep and narrow median incision; upper 

 and lower lateral lobes similar, upper ones slightly 

 smaller than lower ones, subquadrate with retuse mar- 

 gins and rounded angles; semicells with a protuberance 

 within each of the lateral lobes, with one at the base 

 immediately above the isthmus, and with two smaller 

 ones in the centre (often with a large scrobiculation 

 between them). Side view of semicell elongate-pyra- 

 midate, with rectangular basal angles and a dilated, 



" o o 



convex apex ; lateral lobes rotund-rhomboidal, with 

 somewhat retuse margins, upper angle of upper lateral 



]obe rarelv emaroinate. Vertical view broadly elliptic, 



/ ,' 



poles narrow and rounded, sides with four protuber- 

 ances and a fifth one between and beneath the two 

 central ones ; polar lobe oblong elliptical, with convex 

 sides, emarginate poles, and rounded angles. Cell- wall 

 finely punctate. 



Zygospore globose, closely covered with numerous 

 mamillate projections. 



Length 144-205 p, ; breadth 74-107 /x; breadth of 

 isthmus 20-3 1 /x ; thickness 46-65 /x ; cliam. zygosp. 

 without mamillate projections 92-123 /x ; length of 

 mamillas 7*5-9 /x. 



ENGLAND. Cumberland \ Westmoreland !, (Ealfs). 

 AY., X. and E. Yorks. (zygospores from Pilmoor, N". 

 Yorks) ! Lancashire ! Cheshire (Rolfs). Leicestershire 



