2 1 2 NOSTOCHINE^E. PART n. 



division of their filaments ; the segments escape from the 

 gelatinous mass, move slowly in the direction of their 

 length, after a time come to rest, secrete a gelatinous 

 envelope, and not only grow in length by transverse 

 bisection, but split longitudinally into new filaments 

 which are separated by their gelatinous secretions. 

 These movements, discovered by M. Thuret, are evidently 

 intended to disperse the plant. 



Vesicular cells, destitute of endochrome, sometimes 

 furnished with cilia, and of a larger size than the others, 

 are occasionally seen at the end or middle of a filament 

 of the Nostocs, sometimes situated at intervals along 

 their length ; and near to these are sporangial cells, a 

 little larger than the ordinary cells. From analogy, it 

 is believed that the vesicular cells are antheridia, and 

 that the sporangial cells contain germs which, after being 

 fertilized by the spermatozoids, are set free and become 

 resting spores. In some species, the sporangial cells 

 are oblong, and contain vividly green matter ; in others, 

 the cells are elliptical and brown. 



The species are widely distributed. Hormosiphon arc- 

 ticus, a species consisting of a modification of cellulose, 

 abounds to such a degree in the herbless polar regions, 

 that it affords a welcome variety of food. Each plant 

 lies on a small depression of the snow, which covers the 

 soft and almost boggy slopes bordering the arctic seas, 

 but it is carried by the winds in every direction, rolling 

 over the snow and ice to a distance of several miles. Two 

 northern species of Nostoc were found by Dr. Hooker in 

 Kerguelen's Land, growing on wet rocks near the sea ; 

 one of them was the common Nostoc commune. Other 

 species occur in the warm springs in India, as well as in 

 the arctic and antarctic regions, and an aquatic species is 

 much used in China as a wholesome food. The genus 

 Monormia forms floating masses of jelly on the surface 

 of brackish water. The necklaces are of vast length, and, 



