EUASTEITM. 51 



laterally expanded, with an undulation between the 

 base and the upper apiculation on each side. 



Length 57 ^ ; breadth 30 p. 



ENGLAND. Loughrigg, Westmoreland (Bennett). 

 New Forest, Hants (Bennett). 



31. Euastrum binale (Turp.) Ehrenb. 

 (PL XXXVIII, figs. 28, 29.) 



Heterocarpella binalis Turp., 1820 ; Aper<ju organograph. 1828, p. 315, 

 t. 13, f. 17 (figure bad) ; Kiitz. Syn. Diat. 1834, p. 598. 



Cosmarium binale (Turp.) Menegh. Synops. Desin. 1840, p. 221. 



Euastrum binale (Turp.) Ehrenb. Berlin. Monatsber. 1840, p. 208 ; Hass. 

 Brit, Freshw. Alg. 1845, p. 384, t. 91, f. 4-5 ; Ealfs, Brit. Desui. 1848, 

 p. 90, t. 14, f . 8 b, e, and h ; Arch, in Pritch. Infus. 1861, p. 730 ; Eabenh. 

 Flor. Europ. Algar. Ill, 1868, p. 186 ; Lund. Desm. Suec. lb"l, p. 22, 

 23 : Delp. Desm. subalp. 1873, p. 107, t. 6, f. 9-10 ; ? Wolle, Desm. U. S. 

 1884, p. 107, t. 27, f. 23, 24; Cooke, Brit. Desm. p. 75, t. 35, f. 6 a-d ; 

 Hansg. Prodr. Algenfl. Bohm. 1888, p. 207, 252 ; West, Alg. W. Ireland, 

 1892, p. 139 ; Alg. Eng. Lake Distr. 1892, p. 723 ; Eoy & Biss. Scott. 

 Desm. 1883, p. 176 ; N ordst. Index Desm. 1896, p. 59 ; West & G-. S. 

 West, Alg. S. England, 1897, p. 484 ; Alga-fl. Yorks. 1900, p. 64 ; Alg. 

 N". Ireland, 1902, p. 29. 



Didymidium (Euastrum) binale Reinsch, Algenfl. Frank. 1867, p. 138. 



Euastrum binale a. typicum Kirchn. Alg. Schles. 1878, p. 159. 



Helierella binalis Kuntze, Eevis. gen. plant. 1891, p. 898. 



Euastrum binale forma a. minuta Turn. Freshw. Alg. E. India, 1893, p. 81 

 t. 10, f. 50 (Ealfs I.e. f. 8e). 



E. binale forma b. ventricosa Turn. I.e. p. 81 (Ealfs, I.e. f. 8 b). 



Cells minute, about 1-J- times longer than broad, 

 deeply constricted, sinus narrowly linear ; semicells 

 subpyramidate, basal angles broadly rounded, entire, 

 upper part of lateral margins concave; apex broad 

 and truncate, retuso-emarginate in the middle, upper 

 angles dilated to form a minute apiculus. Side view 

 of sernicell ovate, apex acutely rounded, with a slight 

 protuberance near the base on each side. Vertical 

 view elliptic, poles acute, with a small, rounded pro- 

 tuberance at the middle on each side. Cell-wall smooth. 



Zygospore globose, furnished with simple, somewhat 

 blunt spines. 



Length 15-30 /i; breadth 12'5-21/,i; breadth of 

 isthmus 3-8*5 /A; thickness 9-13 ^ ; cliam. zygosp. 

 without spines 20-26 \L ; length of spines 5-7 JJL. 



ENGLAND. Cumberland! AYestmoreland ! (Ealfs). 

 AY., N., and E. Yorks (zygospores from Widdale Fell, 



