MICRASTERIAS. 113 



Large specimens (over 300 ju in. length) were frequent in the 

 above-mentioned lake. The largest form we have seen from 

 the United States measured: length 271 jii; breadth 230 ^u; 

 breadth of isthmus 28 /u. 



15. Micrasterias radiata Hass. 

 (Plate LII, figs. 1-9.) 



Micrasterias melitensis Ralfs in Ann. Mag. Nat. Hist. 1844, xiv, p. 260 

 t. 6, f. 2. [Not M . melitensis Menegh. 1S4<Q == Euastrum Crux-melitensis 

 Ehrenb. 1832 = M. Crux-melitensis (Ehrenb.) Hass. 1845.] 



M.radiata'H.BSs. Brit. Freshw. Hass. 1845, p. 386, t. 90, f. 2 [figure bad]. 



M. furcata Kalfs, Brit. Desm. 1848, p. 73, t, 9, f. 2 [Not H. furcata Ag. 

 1827] ; Arch, in Pritch. Infus. 1861, p. 726 ; Nordst, Desm. Bras. 1870, 

 p. 220, t. 2, f. 13 ; Lund. Desni. Suec. 1871, p. 14; Kirclm. Alg. Schles. 

 1878, p. 161 ; Wolle, Desm. U. S. 1884, p. Ill, t. 35, f . 5, 6 ; Cooke, Brit. 

 Desm. 1886, p. 55, t. 21, f. 1; Hansg. Prodr. Algenfl. Bohui. 1888, 

 p. 208 ; West, Freshw. Alg. Maine, II, 1891, p. 354 ; Alg. W. Ireland, 

 1892, p. 133 ; Johnson, Species of Micrasterias, 1894, p. 58, t. 6, f . 7-14 ; 

 West & G-. S. West, Some N. Amer. Desm. 1896, p. 239 ; Nordst. Index 

 Desm. 1896, p. 126 ; West & GK S. West, Some Desm. U.S. 1898, p. 295 

 (cum fig.) ; Alg. N. Ireland, 1902, p. 30; Scott. Freshw. Plankton, I, 

 1903, p. 526. 



M. melitensis Menegh. var. gracilior Kutz. Spec. Alg. 1849, p. 170. 



Didymidium (Micrasterias) furcatum C furcatum Eeinsch, Algenfl. Frank. 

 1867, p. 144. 



Micrasterias Crux-melitensis (Ehrenb.) Hass. b. furcata Eabenh. Flor . 

 Etirop. Algar. Ill, 1868, p. 190. 



M. pseudofurcata Wolle in Bull. Torr. Bot. Club, 1881, p. 1, t. 6, f . 3 ; 

 Desm. TJ. S. 1884, p. Ill, t. 35, f. 4 ; Lagerli. Biclr. Anier. Desni.-fl. 1885, 

 p. 231. 



M. furcata Ealfs var. decurta Turn. New and Rare Desni. 1885, p. 936 

 t. 16, f. 10. 



M. furcata Ealfs var. simplex Wolle in Bull. Torr. Bot. Club, 1885, p. 128, 

 t. 51, f. 6, 7. 



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



H. pseudofurcata Kuntze, 1. c. p. 899. 



Micrasterias furcata Ealfs a typica Turn. Freshw. Alg. E. India, 1893 

 p. 93, t. 5, f . 5 a. 



M. furcata /3 gracillima Turn. 1. c. f . 5 b. 



M. furcata y expansa Turn. 1. c. f . 5 c. 



Cells of medium size, usually a little longer than 

 broad (but sometimes broader than long), very deeply 

 constricted, sinus widely open with an acute apex; 

 semicells 5-lobed, incisions between the lobes wide and 

 fairly deep ; polar lobe with subparallel sides in the 

 lower half, dilated upwards, with each angle produced 

 into a long, narrow, diverging process with a deeply - 

 furcate apex ; lateral lobes commonly equal, but sub- 

 ject to great variation, normally divided into two long, 



VOL. II. 8 



