THE PAGE OF NATUBE. 



159 



tribes of plants, and especially the changes which take 

 place during the very early or embryonic condition of 

 the more complicated structures. 



The Nostoc (Fig. 22), one of the species belonging to > 

 this strange class of plants, is interesting on account of 

 the historical associations connected with it. It occurs 

 in the form of a greenish jelly or slimy mass on 

 gravelly soils, rocks, pastures, and roadsides, among grass 

 and moss, especially in moist weather. It is widely dis- 

 tributed, occurring as far south as the Antarctic regions, 

 several species having been found by Dr. Hooker on wet 

 rocks near the sea in Kerguelen's Land. It ranges, on 



FIG. 22. NOSTOC COMMUNE. 



the other hand, as far north as Baffin's Bay, and the 

 shores of the Polar Ocean, growing on the soft, boggy 

 slopes of the sea-shore, from whence it is drifted . about 

 by the wind in detached masses, and forming the only 

 vegetable production of any importance over many 

 square leagues. Dr. Sutherland, in his fascinating 

 journal, relates that it has often been found in great 

 abundance on floating icebergs, and in small depressions 

 in the snow upon the ice, at a distance of ten miles from 

 the land. It affords a welcome food, far more palatable 

 than the tripe de roche, the only other edible substance 



