MICRASTERIAS. 385 



62. MICKASTERIAS Ag. 



Char. Frond compressed, deeply divided into two segments. 

 Segments lobed, radiant, and incised. 



Derivation. From fjuucpos, small, and a<Trepias, starred. 



The flat and orbicular fronds, and the radiant and incised 

 lobes, will distinguish this at once from all other genera of 

 Desmidece. 



The genus Micrasterias of Agardh differs entirely from the 

 Micrasterias of Ehrenberg, which has been referred to the 

 Pediastrum of Meyen. 



1. MICRASTERIAS ROT ATA Ag. 

 Plate XC. Fig. 1. 



Char. Fronds smooth, orbicular, ten-lobed. Lobes cuneate, 

 approximate, the end lobe emarginate, the others bifid, the 

 divisions being notched. 



Micrasterias rota Menegh., Synops. Desmid. in Linnaea, 

 1840, p. 215. Echinella rotata Grev., in Hook. Br. 

 Flora, vol. ii. p. 398. (1830). Eutomia rotata Harv., Br. 

 Alg. p. 187. Euastrum rota Ehr., Infus. p. 167. tab. 12. 

 fig. 1.; Pritch. Infus. p. 195. figs. 121123. ; Bailey, 

 American Bacillaria, pi. i. fig. 22. and fig. 24. Micra- 

 sterias Ag., Bot. Zeit. 1827. ? Cosmarium stellinum et 

 C. truncatum Corda, Almanac de Carlsbad, 1835, p. 206. 

 pi. ii. pp. 22,23. ', Ralfs, in Annals, vol. xiv. ; Jenner, in 

 loc. cit. p. 198. 



Hob. Frequent in Sussex: Mr. Jenner. Henfield: Mr. 

 Borrer. About Barmouth : Rev . T. Salwey. Aber- 

 deen : Dr. Dickie. Stevenston, Ayrshire : Rev. D. 

 Landsborough. Penzance ; Dolgelly ; &c. : Mr. Ralfs. 

 Cheshunt Common : A. H. H. 



The frond of this species in its young condition differs so 

 much from the adult form that it might be easily regarded as 

 a distinct production, the lobes being neither bifid nor den- 

 tated. 



c c 



