116 BRITISH DESMIDIACE^E. 



16. Micrasterias Crux-melitensis (Elirenb.) Hass. 



(PI. LIII, figs. 1-3.) 



Euastrum Crux-melitensis Ehrenb. Entwick. Lebencls. d. Infus. 1832, 

 p. 82; Infus. 1838, p. 161, t. 12, f. Ill; Kiitz. Phycolog. germ. 1845, 

 p. 134. 



Cosmarium Crux-melitensis Cordain Aim. de Carlsbad, 1839, p. 243. 



Micrasterias melitensis Menegh. Synops. Desm. 1840, p. 216; Kiitz. spec. 

 Alg. 1849, p. 170. 



Micrasterias Crux-melitensis (Ehrenb.) Hass. Brit. Freslrw. Alg. 1845, 

 p. 386, t. 90, f. 7 ; Ralfs, Brit. Desm. 1848, p. 73, t. 9, f . 3 ; De Bary, 

 Conj. 1858, p. 41 ; Arch, in Pritch. Infus. 1861, p. 726, t. 1, f. 22; Buln. 

 in Hedwigia, 1862, p. 57, t. 10, f. 1 [forms] ; Rabenh. Flor. Europ. Alg. 

 Ill, 1868, p. 190 ; Delp. Desm. subalp. 1873, p. 87, t. 4, f. 7 ; Kirchn. 

 Alg. Schles. 1878, p. 161 ; Turn. Alg. Strensall Common, 1883, f . 23 ; 

 Wolle, Desm. U.S. 1884, p. Ill, t. 35, f. 3 ; Cooke, Brit. Desm. 1886, 

 p. 55, t. 21, f . 2 ; Hansg. Prodr. Algenfl. Bohrn. 1888, p. 208, f . 118 ; 

 Hauptfl. Zellm. u. Hiillgallerte Desm. 1888, p. 93, t. 3, f . 25, 26 ; De 

 Toni, Syll. Alg. 1889, p. 1113; Benn. Freshw. Alg. Hamps. and Devon, 

 1890, p. 7, t. 1, f. 13 [figure very bad] ; West, Alg. W. Ireland, 1892, 

 p. 133 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott. Desm. 

 1893, p. 173 ; Nordst. Index Desm. 1896, p. 90"; West & G. S. West, 

 Alga-fl. Yorks. 1900, p. 67. 



M. Crux-melitensis var. superflua Turn. Some New and Rare Desm. 1885, 

 p. 936, t, 15, f. 11. 



Helierella Crux-melitensis Kuntze, Revis. gen. plant. 1891, p. 897. 



Cells of moderate size, a little longer than broad, 

 very deeply constricted, sinus open with acute or 

 linear apex ; semicells 5-lobed, interlobular incisions 

 widely open, those on each side of the polar lobe 

 much deeper than those between the superior and 

 inferior lateral lobes; polar lobe subquadrate in its 

 lower half, upper half dilated, apex widely retuse, 

 angles produced into short diverging processes with 

 emarginate-bidentate apices ; lateral lobes divided into 

 two short, slightly diverging, elongate-quadrate lobules, 

 emarginate-bidentate (sometimes tridentate or quadri- 

 deiitate with a median notch) at the apex. Vertical 

 view subrhomboid-elliptical, with slightly produced 

 poles. Cell-wall smooth or very delicately punctate. 



Zygospore unknown. 



Length 107-126 /x; breadth 98-118 p; breadth of 

 isthmus 16-19 p.; iDreadth of polar lobe (maximum) 

 35-43 p. 



ENGLAND.- -Ambleside (Ealfs) and Bowness !, West- 

 moreland. Strensall ! (Turner) and Pilmoor ! , IN". Yorks. 



