234 NEMATOGENZ. 
VI. Verrucosa. Species aquatic. Fronds rounded or discoid, 
filled, then hollow, with a tough periderm. 
Nostoc verrucosum. Vawch. Conf. 225, t. xv1., f. 3. 
Fronds subglobose or nodulose, warted, brownish-green, jelly 
tolerably soft, limited at the circumference by a firm and tough 
periderm. 
Trichomes slender, somewhat 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. Rabh. 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 Arr.i., 351. Kutz. Tab. Phye. 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 nivale, Kutz. Tab. Phye. ii., t. 8, f. 4. 
Nostoc Peloponnesiacum, Kutz. Tab. Phyc. ii., t. 9, f. 3. 
Nostoc sphericum, Meneg. Nost. Ital.110. Kutz. Tab. Phyc. 
ii, t. 3, £2. 
Tremella verrucosa, Huds. Fl. Ang. Lightf. Fl. Scot. 898, 
With. Arr. iv., 81. 
In streams, attached to stones. 
Plate XCH. fig. 10. Nostoe verrucosum, natural size; fig. 11, tri- 
chomes x 400; figs. 12-13, portions of trichome; fig. 14, hormogones 
undergoing division ; figs. 12 to 14 x 600, after Thuret ; fig. 16, spores; 
fig. 17, spore in germination x 600. 
Genus 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. MHeterocysts intercalated in the trichomes. 
Spores originating in cells not adjoining the heterocysts.— 
Born. and Thur, Notes Alg. 
Recent authors have modified this genus in different directions. Borzi 
does not adopt the same limitations as Thuret, neither does Kirchner or 
Professors Nordstedt and Wittrock. 
