EUASTRUM. 19 



8. Euastrum ampullaceum Ralfs. 

 (PI. XXXV, figs. 8-10.) 



nii.i.Un<:t'iirii Ralfs, Brit. Desni. 1848, p. 83, t. 13, f. 4 (Euastrum 

 without name figured in Hass. Brit. FresliAv. Alg. 1845, t. 90, f. 11) ; 

 Arch, in Pritch. Infus. 1861, p. 729; Rabenh. Flor. Europ. Algar III, 

 1868, p. 183 ; Delp. Desin. siibalp. 1873, p. 104, t. 6, f. 3, 4; Kirchn. Alg. 

 Schles. 1878, p. 158 ; Cooke, Brit. Desm. 1886, p. 68, t. 33, f. 3 ; Hansg. 

 Prodr. Alo-enfl. Bohm. 1888, p. 205 ; De Toni, Syll. Alg. 1889, p. 1091 ; 

 West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 

 722 : Roy & Biss. Scott Desin. 1893, p. 175 ; Nordst. Index Desm. 1896, 

 p. 44; West & G-. S. West, Alg. S. England, 1897, p. 483; Alga-fl. 

 Yorks. 1900, p. 61 ; Alg. N. Ireland, 1902, p. 28. 



E. ampullaceum forma scrobiculata Nordst. Norges Desm. 1873, p. 8. 



Helierella ampullacea Kuntze, Revis. gen. plant. 1891, p. 898. 



Cells of medium size, a little more than 1-J- times 

 longer than broad, very deeply constricted, sinus 

 narrowly linear and dilated at the extremity; semi- 

 cells three-lobed ; polar lobe cuneate and dilated, with 

 rounded angles, apex convex with a deep and narrow 

 median incision ; lateral lobes much larger than the 

 polar lobe, triangular with rounded basal angles, 

 superior margin of the lobes with a mamillate projection, 

 which is sometimes reduced to a rounded elevation ; 

 semicells with three protuberances across the base, the 

 median one being emarginate, and with two across the 

 centre, also with three conspicuous scrobiculations dis- 

 posed between the five protuberances. Side view of 

 semicell elongate-pyramidate, basal angles rectangular 



I i/ 7 _ O O 



and basal part of margins slightly retuse, upper part 

 of margins somewhat concave, apex rounded. Vertical 

 view pointed-elliptic, with four protuberances on each 

 side and a fifth between and beneath the two central 

 ones ; mamillate projection of lateral lobes widely 

 emarginate ; polar lobe rectangular, with subacute 

 angles and retuse sides. Cell-wall finely scrobiculate. 



Zygospore globose or ovoid-globose, ornamented 

 with numerous mamillate projections. 



Length 93-110/x; breadth 57-59 /i ; breadth of 

 isthmus 14-17*5^; thickness 34-36 ft; diam. zygosp. 

 without mamillate projections 54-72 {JL ; length of 

 mamillae 5 6'4 p. 



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



