A STUDY OF RELATIONS BETWEEN PLANT GROWTH. 



349 



But note the extremely small amount of nitrate required to support a 

 rapidly growing and later very dense vegetation as shown by the followng 

 analyses : 



Note also that the next lower form of combined nitrogen was likewise 

 extremely low. Yet these stations contained the very densest vegetation 

 to be found in the entire lake. Analyses at different depths show that the 

 nitrogen content was practically the same from top to bottom in these 

 stations. Hence samples taken from near the surface were trustworthy. 

 The following two vertical series show this clearly. • 



From the fact that the regions of greatest plant growth are the regions 

 of lowest content of available nitrogen it would seem that nitrogen content 

 of itself can not be a determining factor of great importance. This 

 rather radical statement is to be tempered somewhat in consideration 

 of the fact that most of the increase of plant growth was made before the 

 nitrate went so low. A look at the data will show, however, that some in- 

 crease was made after July 1, when nitrate was .09* parts per million and a 



♦After an analysis indicates that the analysis was carefully checked. 

 8432—23 



