NOSTOCEJS. 237 



Anabaena circinalis, Phillips in Grevillca ix., p. 4, t. 134, 

 figs, e, /, g. 



In ditches with Confervce, and floating on lakes. 



" Floating like powdered verdigris on mountain lochs." This species 

 seems to be variable in the form and size of the spores, and in the number 

 of vegetative cells which occur between the heterocysts and spores. 

 Wittrock has figured varieties in which two, or even sometimes one, 

 cell intervenes between the heterocyst and spore, alluding to the fact 

 that in English specimens they are sometimes in juxtaposition. Al- 

 though technically the Shropshire specimens would seem to belong to 

 Sphcerozyga, yet in all other features they agree so well with this species 

 that we have cited them here as abnormal forms of the present species. 



Plate XC 111. Jig. 3. Portions of trichomes with heterocysts and 

 spores X 400 ; b, after Kalfs ; c, after Phillips. 



Anabaena Ralfsii. (Ruiz.) 



Forming extensive strata of a velvety rich dark green colour, 

 sometimes verging towards verdigris green. 



Trichomes moniliform, joints sphserical. Heterocysts ellip- 

 tical, spores elliptic or cylindrical, one or two in each series 

 not contiguous to the heterocysts. 



SIZE. Cells -004 mm. diam. Heterocysts -005--006 x 008 

 mm. Spores -008--01 x -022--03 mm. 



SpTicsrozyga Ralfsii (Thw.) Eabh. Alg. Eur. ii., 193. Kirch. 

 Alg. Schl. 237. 



Doliclwspermum Raljsii, Ann. Nat. His. 1850, t. 9, f. 2. 



Cylindrospermwn Ralfsii, Kutz. Tab. Phyc. t. 98, f. 7. 



In bogs and rivulets. 



" Distinguished from A. intequalis by its elliptical heterocysts (which 

 are comparatively less broad), by its more orbicular ordinary joints, and 

 by having fewer spores." Ralfs. 



Plate XCIV. 'fig. 1. Trichomes with heterocysts and spores X 400 

 diam. 



Anabaena Smithii. (7 Ait;.) Nord. $ Wittr. Alg. Exs. No. 197. 



Trichomes straight, each included in a definite gelatinous 

 sheath ; joints sTibsphserical, compressed, about as long as wide ; 

 heteroeysts subsphserical somewhat barrel shaped, half as wide 

 again as the joints, puncta very distinct ; spores cylindrical, very 

 unequal in length, with the ends rounded and somewhat trun- 

 cate. 



SIZE. Cells -004--006 mm. diam. Heterocysts -008--009 x 

 009--013 mm. Spores -009--012 x -02--04 mm. (Wittrock.) 



Dolichospermum /Smithii, Thwaites Ann. Nat. Hi*t. IboO, t. 9, 

 f. 4. 



In boggy pools with other Alga?. 



