NOSTOCHINE^. 113 



NOSTOC. Vauch. 



Frond gelatinous or coriaceous, globose or lobed, filled with curled, beaded, simple 

 filaments, formed of spherical or ellipsoidal coloured cells, interrupted here and there by 

 a colourless cell of larger size. Spores formed from the ordinary cells. (On damp 

 ground or in fresh water.) 



1. NosTOC commune, Vauch. ; terrestrial ; frond expanded, membranaceous, plaited 

 and waved or curled, olive-green, polymorphous. Vauch. Tab. 16. Fig. 1, Ag. Syst. 

 p. 18. Harv. Man. Ed. 1, p. 183. Hass. Br. Fr. W. Alg. p. 288 t. 74,/. 2. 

 Kiltz. Sp. Alg. p. 298. 



Hab. On damp soil, in autumn. Common after rain on dry flats, Rio Bravo, Dr. 



Schott. (v. v.j 



In dry weather the frond curls up and contracts, looking like a piece of shrivelled 

 skin, and in that state may be blown about without injury. When moistened it expands, 

 and then forms a semi-transparent, semi-gelatinous, elastic membrane, of a dull bottle- 

 green colour. Under the microscope it appears like a transparent jelly traversed in 

 every part with curled strings of beadlike, green cells. 



2. NosTOC (Hormosiphon) arcticum, Berk. ; fronds foliaceous, variously plaited, green 

 or brownish ; filaments at length (their gelatinous envelope being dissolved) free. 

 Berk, in Proc. Lin. Soc.Jide An. Nat. Hist. 2d Ser. vol. 10, p. 302. 



Hab. On the naked soil, in boggy ground. Assistance Bay, lat. 75° 40' N. Dr. 

 Sutherland, (v. s.) 



" Fronds foliaceous, variously plicate, sometimes contracted into a little ball. Gela- 

 tinous envelope at length effused ; connecting cells at first solitary, then three together ; 

 threads, which are nearly twice as thick as in N. commune, breaking up at the con- 

 necting cells, so as to form new threads, each terminated with a single large cell, the 

 central cell becoming free." Berk. I. c. 



" It grows," says Dr. Sutherland, " upon the soft and almost boggy slopes around 

 Assistance Bay ; and when these slopes become frozen at the close of the season, the 

 plant lying upon the surface in irregularly plicated masses becomes loosened, and if it 

 is not at once covered with snow, which is not always the case, the wind carries it about 

 in all directions. Sometimes it is blown out to sea, where one can pick it up on the 

 surface of the ice, over a depth of probably one hundred fathoms. It has been found at 

 a distance of two miles from the land, where the wind had carried it. At this distance 

 from the land it was infested with Podurte, and I accounted for this fact by presuming 

 that the insects of the previous year had deposited their ova in the plant upon the land, 

 where also the same species could be seen in myriads upon the little purling rivulets, 

 at the side of which the Nostoc was very abundant." At p. 205 of his Journal, Dr. 



Q 



