234 NEMATOGEN.E. 



VI. VERRUCOSA. Species aquatic. Fronds rounded or discoid r 

 filled, then hollow, witli a tough periderm. 



Nostoc veirmcosum. VancJi. Conf. 225, t. xvi., /. 3. 



Fronds subglobose or nodulose, warted, brownish-green, jelly 

 tolerably soft, limited at the circumference by a firm, and tough 

 periderm. 



Trichomes slender, somewliat compact, spaced out, and a, 

 little flexuous at the centre, more compact and distorted at the 

 periphery, where they are often deprived of sheaths. Joints 

 subglobose, closely connected. Heterocysts spherical. 



SIZE. Joints '003-'0035 mm., heterocysts -006 mm., spores 

 005--007 mm. 



Born. & Thuret Notes Alg. p. 117. Thur. Ann. Sci. Nat. 

 1844, ii., t. 9, f. 1-5. Eabh. Alg. Eur. ii., 176. Borzi Alghe 

 Fico. p. 284. Hass. Alg. 291, t. 76, f. 1. Grev. Fl. Ed. 323. 

 Hook. FL Scot, ii., 74. Mack. Hib. 245. Fl. Dev. ii., 49. 

 Gray AIT. i., 351. Kutz. Tab. Phyc. ii., t. 9, f. 11. Eng. FL 

 v., 400. Harv. Man. 183. Dickie Bot. Guide, 310. 



Nostoc irregulare, Wartm. in Rabh. Alg. Eur. ii., 167. 



Nostoc nival e, Kutz. Tab. Phyc. ii., t. 8, f. 4. 



Nostoc Peloponnesiacum, Kutz. Tab. Phyc. ii., t. 9, f. 3. 



Nostoc splicericum, Meneg. Nost. Ital. 110. Kutz. Tab. Phyc. 

 ii., t. 3, f. 2. 



Tremella verrucosa, Huds. Fl. Aug. Lightf. Fl. Scot. 898, 

 With. AIT. iv., 81. 



In streams, attached to stones. 



Plate XCII. fig. 10. Nostoc verrucosiim, natural size ; fig. 11. tri- 

 chomes x 400 ; figs. 12-13, portions of trichome ; fig. 14, horrnogones 

 undergoing division ; figs. 12 to 14 x 600, after Thuret ; fig. 16, spores; 

 fig. 17, spore in germination x 600. 



GEN PS 95. ANABAENA. Bory. (1823.) 



Trichomes moniliform, without sheaths (or rarely vaginate), 

 composed of sub-globose cells, some of which become changed 

 into globose or elongated spores, usually yellowish brown or 

 golden brown. Heterocysts intercalated in the trichomes. 

 Spores originating in cells not adjoining the heterocysts. 

 Born, and Thur. Notes Alg. 



Eecent authors have modified this genus in different directions. Borzi 

 does not adopt the same limitations as Thuret, neither does Kirchuer or 

 Professors Nordstedt and Wittrock. 



