244 NEMATOGEN.E. 



SIZE. Cells -003 -'004 mm., heterocysts rather longer. 

 Spores -014 x '025--03 mm. 



Kirch. Alg. Schl. 237. Kabh. Alg. Eur. ii., 186. 

 Anabaina impalpeb rails, Hass. Alg. 283, t. 75, f. 3. 



In ditches and ponds. 



Plate XCV. fig. 1. Trichomes with heterocysts and spores X 400. 



Cylindrospermum catenatum. Ralfs Ann. Nat. Hist. t. 8,f. 14. 



Stratum bluish green. Trichomes very fine elongated 

 straight, or slightly flexuous, generally parallel, moniliform. 

 Joints sphserical minute. Heterocysts oval. Spores 2-8 in 

 each series, at first spherical, then more or less oval, but little 

 broader than the heterocysts. 



SIZE. Cells about -003 mm., heterocysts a little longer, 

 spores about '006 x '008 mm. 



Rabh. Alg. Exs. No. 1358. 



In fresh water. 



Clearly distinguished from the preceding species by its nu- 

 merous spores. 



Plate XCV. Jig. 2. Trichomes with heterocysts and spores X 400. 



GENUS 99. NODULAR! A. Mertens. (1822.) 



Trichomes distinctly vaginate, with very closely compressed 

 disc-shaped joints, collected in a gelatinous or menibranaceous 

 irregularly diffused stratum. Heterocysts intercalated at re- 

 gular intervals, vegetative joints nearly equal, transversely 

 compressed. Spores fuscous, or golden yellow, becoming tawny, 

 globose, slightly compressed. 



Nodularia litoiea. (Thw.) Thur. Ann. Sci. Nat 1875, 378. 



Scarcely gelatinous, forming a deep green fleecy covering to 

 floating plants on which it occurs. Trichomes of considerable 

 diameter, nearly straight. Joints of a beautiful blue green 

 colour, very short and compressed, giving the filaments the ap- 

 pearance of an Oscillaria. Heterocysts pale reddish. Spores 

 elliptical, at length acquiring a deep brown colour. 



SIZE. Trichome, without sheath, -012 mm. 



Born, and Thur. Notes Algol, ii., 121, t. 29, f. 1-9. 



Spermosira litorea, Kutz. Phy. Gen. 213. Rabh. Alg. Eur. 

 ii., 186. Harv. Phy. Britt. t. 113, f. c. 



In muddy, brackish ditches. 



