1 86 FIXATION OR ASSIMILATION OF NITROGEN 



the algae in turn obtaining some or all the nitrogen they 

 need for nutrition from their associates. 



Stoklasa states that the " Alinit " bacillus fixes atmo- 

 spheric nitrogen in considerably larger amounts in the 

 presence of species of Stichococcus and Nostoc than when 

 these algae are absent. He also notes that soils contain- 

 ing an abundance of algae are richer in bacteria than 

 those which are poor in algae, and that Pleurococcus and 

 Nostoc contain 6 to 7 per cent, of pentose, 70 per cent, of 

 which is soluble in water, and easily available for the 

 nutritive requirements of bacteria. 



