OSCILLATORIA. 249 



meter, coated with a frequently interrupted covering of a 

 dull glaucous green hue, under which the thread itself ap- 

 pears of a lighter glaucous bluish colour, very even in thick- 

 ness and surface, consisting of scarcely distinguishable joints, 

 about as broad as they are long." — Sm. 



6. OSCILLATORIA iERUGESCENS Drum. 



Plate LXXIL Fig. 2. 



Char. Stratum o/" a ^?ze deep green, highly gelatinous ; xohen 

 dried, ceruginous blue, and glossy. Filaments slender, 

 opaque green. Stria3 evident. 

 Druramond, in Ann. Nat. Hist. vol. i. p. 1 . ; Manual of 



Brit. Alg. p. 163. 

 Hab. Lakes of Glaslough, co. Monaghan, Ireland: Dr. 

 Drummond. Farnham : Mr. Jenner. Bottom of pools 

 near Stocket, Aberdeen : Dr. Dickie. 



" Filaments exceedingly slender, opaque green ; conglom- 

 erated in large toughisli glutinous masses, in sheltered, calm 

 situations, and rarely floating on the surface ; in more open 

 exposures, broken into innumerable fragments, and suspended 

 like cloudy flocculi in the water. Stri<z numerous, at dis- 

 tances of about half a diameter from each other. Oscillatory 

 movement often lively. Colour when di'ied, a beautiful 

 a3ruginous blue ; adheres strongly to paper, exhibiting a glossy 

 surface. Filaments expanded by moisture so as to seem re- 

 cent, and sometimes resuming the oscillatoiy motion." — 

 Dr. Drummond. 



This species may at once be distinguished when dried from 

 all others by the peculiarly dense and waxen appearance of 

 the stratum, which also exhibits numerous fissures. The fila- 

 ments are smaller than those of O. tenuis, and the stria; closer. 

 They are likewise brittle, and when dried break up into very 

 short pieces, which arc not of uniform diameter. 



