328 Mr. J. Ralfs on the Nostochinese. 



p. 201. t. 68. fig. D (1819). Anabaina membranina, Bory, Arthr. 

 fig. 7 d (according to Kiitzing) ; Mougeot et Nestler, Stirpes Cryp- 

 togamiae Vogeso-Rhenanae, no. 896. Anabcena Flos-aquce, Trevir. 

 in Linn. 1843, t. 3. fig. 5-7; Kiitzing, Phycologia Generalis, p. 209; 

 Phycologia Germanica, p. 171 ; Species Algarum, p. 289. Sphcero- 

 zyga membranina, Endlicher, Mantissa Bot. Alterum Sup. tertium, 

 p. 12 (1843). Trichormus incurvus, Allman, Annals of Nat. Hist. 

 vol. xi. p. 163. t. 5 (1843) ; Hassall, Brit. Freshwater Algae, p. 285. 

 t. 75. fig. 1. 



Stagnant pools and other still waters. Portmore Lough, Antrim, 

 Mr. W.Thompson ; Ayrshire, Rev.D.Landsborough ; Dolgelley, J.R. ; 

 Oswestry, Shropshire, Rev. T. Salwey ; Grand Canal Dock, Dublin, 

 Professor Allman. 



Finland, Lyngbye ; France, Bory ; Germany, Kiitzing. 



Trichormus Flos-aquce rises to the surface of the water in gela- 

 tinous masses of considerable size, and is generally of a rich 

 bluish green colour. Filaments curved and beautifully monili- 

 form. Cells spherical ; vesicular ones resembling the ordinary 

 ones, but larger and without granular matter. Sporangia I have 

 not detected, but since cells, not different in form from ordinary 

 ones, are often filled with granular matter, there is probably no 

 very obvious difference between the latter and the sporangia. 



Plate VIII. fig. 2. 



2. T. spiralis (Thompson). Filaments coiled or spiral ; ordinary cells 

 subquadrate or orbicular ; vesicular cells and sporangia orbicular. 

 Anabaina spiralis y Thompson in Annals and Mag. of Nat. Hist, 

 vol. v. p. 81 (1846). Spirillum Thompsoni, Hassall, Brit. Fresh- 

 water Algae, p. 278. t. 75. fig. 7 (1845). 



Ballydrain Lake, near Belfast, Mr. Thompson ; Petersfield, Mr. 

 Jenner. 



I regret that the specimens Mr. Thompson has sent me are 

 too imperfect to serve for the identification of the species. I am 

 by no means certain that Mr. Jenner' s plant is identical with the 

 Irish one, and I have referred it to this species in deference to 

 the opinions of Mr. Thwaites and Mr. Jenner, rather than from 

 my own conviction. 



The filament in Mr. Jenner* s specimen is somewhat coarse, and 

 coiled rather than loosely spiral. The ordinary joints are more 

 or less quadrate, the vesicular cells orbicular, and the sporangia 

 similar to the ordinary cells, but larger and more orbicular. 

 Mr. Thompson's figure represents his T. spiralis with perfectly 

 orbicular ordinary cells, and a slender filament which, except in 

 being spiral, scarcely differs from Trichormus Flos-aqua?. 



Plate VIII. fig. 3. a, Mr. Jenner's specimen; b, fragment of Irish spe- 

 cimen with sporangium between ordinary cells ; c, mature sporangium. 



