264 CRYPTOGAMIA ALG.E. 



nules have often seemed to me surrounded with a pellucid 

 ring. 



169. OSCILLATORIA. 



1. O. violacea, mass gelatinous, dark purple ; filaments very 

 slender, straight, without perceptible transverse strize, laid on a 

 thin compact greenish substratum Conferva mucosa, &c. DILL. 

 Hist. Muse. 15. No. 4. 



Hob. Rapid streams. On stones in the bed of a burn be- 

 low the mansion house of Longformacus. July. 



The synonym of DILLENIUS has been usually quoted as be- 

 longing to the Conferva, violacea or alpina of botanists, but 

 the quotation has been made certainly without a critical 

 examination of his description, which is, as is usual with 

 him, very complete, and as accurate as could be done with- 

 out the aid of a microscope. I have no doubt whatever of 

 his plant being identical with the one before me, and I 

 consider myself lucky in refinding and replacing in our 

 systems a species which has been so long lost and mis- 

 understood. It covers the stones in rivulets with thick- 

 smooth jelly-like patches as large as a man's hand, and of 

 a purple or very dark green colour, the difference in hue 

 depending on causes which could not be detected. The 

 masses are soft and gelatinous, and have some resemblance 

 to a piece of congealed blood. The specimens I collected 

 were put into a glass of water for two days previous to 

 their being examined ; and they communicated to the wa- 

 ter a deep purple tint, and gave out a strong animal pu- 

 trid smell. On adding some diluted sulphuric acid to this 

 tincture, the colour was removed, and the smell became 

 ammoniacal. Adheres closely to paper in drying, and 

 dyes it a very fine bluish- purple. 



2. O. viridis, mass thin, gelatinous, verdigris-green ; filaments 

 short, very slender, straight, without perceptible striae, woven 

 into a compact thin bright-green stratum VAUCH. Conf 195. 

 t. 15. f. 7. Osc. tennis, LYNGB. Hydroph. Dan. 88. Oscillaria 

 riridis, Bot. Gall ii. 993. 



Hab. On mud in stagnant water. In the Low below 

 Goswick. April. 



Grows in irregularly circumscribed patches of a very fine 

 green colour. To appearance it would dissolve into its 



