240 NEMATOGENJ2. 



Aphanizomenon flos-aquae. Ealfs Ann. Nat. Hist. i. 9, /. 6. 



Floating, forming a pale or dark blue green stratum on the 

 .surface of the water. Trichornes very thin, nearly straight, 

 aggregated in membranaceous flakes which readily separate, 

 either distinctly or indistinctly articulated, very pale blue or 

 colourless. Joints cylindrical, about as long as broad, slightly 

 granular. Spores more or less elongated cylindrical, 6-12 times 

 as long as broad, granular. 



SIZE. Cells -003-004 mm. diam. Spores -005 x -03--04 

 mm. 



Allman, Quart. Journ. Micr. Sci. 1855, p. 21, t. 3. 



Byssusflos-aquce, Linn. Spec. Plant. (1753) No. 1168. 



Limnochlide flos-aquce, Kutz. Tab. Phyc. i., t. 91, f. 2, a. 



Aphanizomenon incurvum, Morr. Bull. Brux., 1839, Harv. 

 Man. 145, Hass. Alg. 280, t. 76, f. 6. 



Sphcerozyga flos-aquce, Rabh. Alg. Eur. ii., 195. 



In ditches, ponds, and meres. 



One of the species of Algas which contribute to the phenomena cha- 

 racterized as " breaking of the meres," Professor Allman thinks that he 

 has observed heterocysts (see Micr. Journ. p. 22), but this is not con- 

 firmed. 



Plate XC1V. fig. 1. a, Trichomes in bundles, X 200 ; b, Trichomes, 

 with spores X 400. 



GENUS 97. SPHJEROZYGA. (Ac/.) Ealfs. (1850.) 



Trichomes involved in an amorphous, often very quickly 

 diffluent, mucilage, rarely vaginate, agglutinated in an inde- 

 finite gelatinous stratum ; joints sphserical, elliptical or oblong, 

 transversely compressed and often quadrangular. Heterocysts 

 intercalated, binary, or solitary. Spores originating in cells 

 placed on each side of the heterocysts. 



Sphaexozyga Carmichaeli. Harv. Phyc. Britt. t. 113. 



Stratum thin, of a dark or bluish green colour when recent, 

 but opaque and glaucous when dry. Trichomes moniliforni, 

 with tapering extremities ; joints distinct, somewhat quadrate. 

 Heterocysts spherical. Spores oblong. 



SIZE. Cells -OU35--0045 mm. Heterocysts -006 mm. diam. 

 Spores -008--01 X -018--025 mm. 



Kutz. Tab. Phyc. i.,t. 99, f. 4. Ralfs Ann. Nat. Hist. 1850, 

 t. 8, f. 7. Rabh. Alg. Eur. ii., 191. 



Belonia tonilosa, Garni. Eng. Fl. v., 379. Harv. Man. 167. 



On damp soil in salt marshes flooded at spring tides, in 

 brackish ditches, &c. 



