100 



idae, and aquatic and terrestrial phanerogams. In this investi- 

 gation care was taken to exclude causes of error owing: i) to 

 incomplete sterilization of the culture, 2) to the presence of 

 nitrogen compounds of the air and 3) to incomplete development 

 of the plants; factors which were not all taken into consideration 

 by any of the preceding authors in the study of this important 

 problem. 



The cultures were made in flasks and vessels of different 

 shapes, and covered by bell-jars sealed at the bottom, through 

 which measured quantities of sterile air free from nitrogenous 

 compounds were passed. The culture media employed were 

 sterile nutrient solutions, or river sand previously washed with 

 hydrochloric acid, or pure quartz sand, fertilized with the 

 nutrient solutions. The seeds were sterilized before being sown, 

 after having been analyzed to determine the total amount of 

 nitrogen they contained. The same was done with the plants 

 obtained from them, after these had grown for a certain length 

 of time. 



A carefully measured amount of nitrogenous compounds was 

 applied to some plants, while others were cultivated absolutely 

 free from nitrogen. In the first instance the culture medium 

 was again analyzed after cropping the plants. The quantity of 

 nitrogen the plants had assimilated from the air was determined 

 by subtraction. Analyses were also made in various cases of the 

 air contained in each bell-jar where plants had grown ; in other 

 words, it was determined if any decrease in the quantity of the 

 free nitrogen of the air had taken place during the growth of the 

 plants. 



The results obtained showed very clearly that the power of 

 absorbing free nitrogen is more general than was believed, as all 

 of the plants tested had taken up free nitrogen in greater or les- 

 ser quantities from the air in which respiration and assimilation 

 took place. It is a remarkable fact that the plants took up more 

 free nitrogen from the air when the culture medium was supplied 

 with the small quantities of nitrogenous compounds. 



In that part of our paper in which former investigations were 

 considered from a critical standpoint, a discussion of the theory 

 of "albumen generators" of Jamieson was given, demonstrating 

 why this is not acceptable. 



