NOSTOC. 



[ 545 J 



NOSTOC. 



rows of cells (I'l. 8. fig. 7) wliicli iucreaso I found on damp ground, wet rocks, mosses, 



the length by I'epeated transverse sub- 



Nostoc commune. 

 Natural size. 



division ; here and there are larger cells 

 (a, c) which appear brighter than the rest, 

 resembling the iH^sicu/ar cells of the allied 

 genera. The filaments break up after a 

 time into short fragments, which by cell- 



Fig. 528. 









Nostoc caeruleum. , 

 Filaments. Magnified 200 diameters. 



division produce new filaments. The pelli- 

 cle of the frond bursts, allowing the gela- 

 tinous mass to escape, and the filaments to 

 spread abroad in the water ; 

 these consist of short straight- 

 ish pieces, which move slowly 

 along in the direction of their 

 length ; after a time they cease 

 to move, and a new gelatinous 

 envelope is formed around each 

 piece like a transparent sheath. 

 They soon become enlarged 

 considerably, and then divide 

 in the direction of the length of 

 the filament (fig. 520), which 

 becomes so disintegrated that 

 the filament forms a spiral, 

 by the increase of which 

 through further transverse 

 cell-division the mass be- 

 comes confused, until the de- 

 velopment of a greater quan- j^^S'^ms 

 tity. or the gelatmous matter 

 makes the filaments more distinct. 



The Briti.^h species of this genus are 



Nostoe 

 verrucosum. 



Filaments mul- 

 tiplying by 

 8ul)division. 



ifcc, and free or attached to stones, in 

 fresh water (PI. 8. fig. 7). They are very 

 numerous, and the following only can be 

 noticed. 



* Frond globose or sifbr/lobose. 



Nodoc minutissimum. Frond globose, 

 fronr 1-30 to 1-4'" ; filaments equal, deep 

 teruginous green, densely entangled ; peri- 

 derm growing brown. 



N. lichenoides. Fronds from the size of 

 a mustard-seed to that of a pea, aggregated 

 and heaped together ; filaments equal, 

 loosely entangled, ajruginous or olivaceous ; 

 periderm pellucid, colourless, firm. 



ft. ve<icariuin\ larger, soft, wit li a fuscous 

 distinct periderm, mucous within, some- 

 times hollow. 



N. spji(pj-icum. Frond the size of a pea, 

 firm, blackish seruginous or somewhat olive- 

 coloured, soft within ; filaments pale green, 

 loosely entangled ; periderm firm, colourless 

 or fuscescent, subopaque. On stones in 

 mountain rivulets. Meneghini states that, 

 when dried and again moistened, it emits a 

 pleasant odour like violets. Hassall thir.ks 

 it probably an immature form of N.fuli- 

 aceum. 



N. ccerideum. Frond from the size of a 

 pea to that of a sloe, soft and slimy, pale 

 a3ruginous blue ; filaments unequal, loosely 

 entwined, joints oblong-elliptical ; periderm 

 colourless, pellucid, soft. On mosses iu 

 flowing water or very moist places. 



N. pruniforme. Frond the size of a large 

 round plum, deep seruginous green, very 

 soft and watery within ; filaments unequal, 

 bright aeruginous green, loosely entangled, 

 joints subdepressed, dimidiate ; periderm 

 leathery, crystalline ; unattached, iu fresh- 

 water pools or rivulets. 



-** Frond foliaceous, irref/ular, or vesicular. 



JV. foliaceum. Frond terrestrial, mem- 

 branous, erect, plaited, olive-green ; fila- 

 ments slender, copious. On clayey ground 

 constantly moistened bv oozing water. 



N. comnnme (fig. 527, & PI. 8. tig. 7). 

 Frond terrestrial, gelatinous, subcoriaceous, 

 greenish, irregularly plaited ; filaments 

 nearly equal, tiexuous, colourless or green, 

 loosely entangled, the joints loosely con- 

 joined, distant or geminate, subspherical, 

 depressed, with a central opaque spot ; 

 periderm hyaline, srowing brown. Gravelly 

 soils, garden walks, rocks, barren pastures, 

 &c. ; very common iu autumn nnd winter. 



2n 



