230 NEMATOGEN^E. 



Nostoc ellipsosporum. (Desm.) Rabh. Alg. Eur. n., 169. 



Plant terrestrial. Frond plane, applied to the ground by the 

 lower surface, gelatinous, rufous brown. 



Tricbomes densely interwoven, pale a?ruginous green, joints 

 cylindrically elongated, loosely connected, slieatbs broad, homo- 

 genous. Heterocysts elongated, elliptical, spores oblong, 

 smooth. 



SIZE. Joints '004 mm., heterocysts -006--007 mm., spores 

 006 x -006--008 x -019 mm. 



Born. & Thuret Notes Alg. ii., 94, t. xxvii., fig. 7-11. 



Hormosiphon ellipsosporum^ Desm. PL Crypt. No. 133. 



On the ground amongst moss. 



Plate XC. Jig. 8. Trichome of Nostoc ellipsosporum producing spores 

 X 400 ; fig. 9, portion of trichome which at one extremity exhibits the 

 sheath ; fig. 10, trichome with the greater part of the joints transformed 

 into spores ; fig. 11, young trichome from germinating spore. Figs. 9, 

 10, 11, X 600 diam. after Bornet. 



III. HUMIFUSA. Species terrestrial. Fronds at first globose, 

 then confluent, and forming gelatinous patches adhering by their 



lower face. Spores smooth. 



Nostoc muscorum. Ag. Disp. Alg. p. 55. 



Frond dark green, foliaceous, tuberculate, opaque. 



Trichomes diffused, irregularly interwoven, pale geruginous 

 green. Sheaths confluent. Heterocysts spherical, usually 

 intercalated. Spores oval. 



SIZE. Joints -0035 mm., heterocysts -005 mm., spores -006 

 x -01 mm. 



Born. & Thuret Notes Alg. p. 96, t. 27. Rabh. Alg. Eur. ii., 

 173. Eng. Fl. v., 399. Hass. Alg. 292, t. 74, f. 4. Gray 

 Arr. i., 351. 



On calcareous rocks, and the mosses that cover them. 



Plate XC. fig. 12. Nostoc muscorum nat. size ; fig. 13, trichome X 

 400; fig. 14, sterile trichome; fig, 15, fructifying trichome; fig. 17, 

 trichome with spores involved in sheath ; figs. 17, 18, spores germinating ; 

 figs. 14-18, X GOO, after Bornet. 



Nostoc humifusum. Carm. Eng. Fl. n., 399, 



Frond small, at first globose or subglobose, from the size of 

 a peppercorn, olive, then brownish, shining opaque when dry. 



Trichomes olive, slender, vertically folded, sheaths well de- 

 fined. Heterocysts globose. Spores oval. 



SIZE. Joints -0022 mm., heterocysts '003 mm., spores '004 

 x-006 mm. 



