254 NEMATOGEN.E. 



in reality a Lyngbi/a, allied to L. cestuarii, and not a true Oscillaria. 

 We are indebted to Professor Percival Wright for an examination of 

 authentic specimens of this, and several other of Harvey's species. 



Plate XCVllI.Jly. 4. Portion of trichome X 400. 



Doubtful Species. 

 Oscillaria Dickiei (Hass.) Rabli. Alg. Eur. u., 113. 



Stratum pale chesnut-brown, gelatinous, shining ; trichomes 

 of medium size, long, straight, fragile, with visible spaces 

 between the joints. 



SIZE. Not determined. 



Oscillatoria Dickiei, Hass. Alg. 258, t. 72, f. 13. 



Pools of fresh water near the sea. 



The colour of this species is so peculiar as at once to distinguish it 

 from all others which have been described. This colour is preserved in 

 drying; the filaments are of nearly the same diameter with those of 

 0. tennis, but they preserve their calibre when dried. Bassall. 



Oscillaria thermalis. (Hass.) Eabh. Alg. Eur. n., 113. 



Trichomes straight, rigid, fragile, green ; divisions of the 

 joints distinct, rather remote. 

 SIZE. Not determined. 

 Oscillatoria thermalis, Hass. Alg. 250, t. 72, f. 3. 



In warm water. 



The figures and descriptions in Hassall's work are wholly insufficient 

 for the proper identification of this and the following species. 



Oscillaria vizescens (Hass.) Rabh. Alg. Eur. n., 113. 



Stratum pale blue-green ; trichomes of medium size, pale 

 yellowish-green, with the joints rather distant, nearly equal in 

 length to their diameter. 



SIZE. Not determined. 



Oscillatoria virescens, Hass. Alg. 250, t. 71, f. 9. 



On the ground. 



GENUS 102. MICROCOLEUS. Desm. (1823.) 



Trichomes rigid, articulate, crowded together in bundles, 

 enclosed in a common mucous sheath, either closed or open at 

 the apex ; sheath ample, colourless, more or less lamellose, 

 rarely indistinct. = Chthonoblastus, Kutz. (1843.) 



