MONORMIA. 285 



1. TRICHORMUS INCURVUS Allm. 

 Plate LXXV. Fig. 1.? 



Char. fi Plant either diffused through the water or collected on 

 the surface. Filaments of a pea-green colour, crowded 

 together confusedly in a gelatinous matrix, variously curved, 

 but never regularly spiral, assuming, when dried, a fine 

 verdigris-green colour without lustre" Allman. 



Allman in Annals of Nat. Hist. vol. xi. p. 163. 

 Hob. In the Grand Canal dock, Dublin, October: Dr. 

 Allman. 



The only authentic specimen which I have seen of this 

 species was so much injured that I was not able to make an 

 examination of it in the least satisfactory. A specimen, how- 

 ever, sent me by Mr. Thompson, collected by that gentleman 

 and found floating on the surface of Lough Neagh, at Shane's 

 Castle, marked Anabaina fios-aqucK, accords so well with the 

 description and figure given by Dr. Allman of T. incurvus, 

 that scarcely a doubt remains as to the propriety of regarding 

 Mr. Thompson's plant as that species, see PL LXXV. fig. 1. 

 From the true A.fios-aquce Mr. Thompson's specimens differ 

 in the less considerable dimensions of the filaments, and in 

 the absence of the enlarged cells. 



Section ii. 

 Filaments invested in a mucous matrix of a definite form. 



37. MONORMIA Berkeley. 



Char. " Frond branched, composed of a single moniliform 

 thread, following the ramifications, immersed in gela- 

 tine'' Berk. 

 Derivation. From povos, one, and oppos, a necklace. 



This genus scarcely differs from Nostoc, between which and 

 Anabaina it forms a clear link. 



