FIGURES 



Page 



1 Relationship between plant growth and the 

 concentration of an essential element in the 



plant 6 



2 Yield of Elodea as related to total nitrogen 

 concentrations in index segments 15 



3 Growth of Elodea as length increase under 

 adequate and inadequate nitrogen supply 17 



4 Effect of light intensity on Elode a growth 48 



5 Effect of temperature on Elodea growth 49 



VI 



