A STUDY OF RELATIONS BETWEEN PLANT GROWTH 351 



(4) In regions of extremely dense vegetation the nitrate and nitrite 

 were reduced to an extremely low figure after the latter part of July. 



(5) The nitrate supply for the growing plants need not be preformed, 

 provided there is a supply of the more complex compounds upon which 

 bacteria may work and so produce the simpler forms required for plant as- 

 similation. 



(6) The albuminoid and ammonia content of the water serves as a 

 storehouse from which the simpler forms are made by oxidation processes. 

 The sediment of the bottom serves in the same way. Stirring of the water 

 produces great variations in the content of the albuminoid and ammonia. 



(7) Plants may flourish in water containing an extremely small amount 

 of nitrate and nitrite, provided the conditions for producting these forms 

 are present. 



(8) Sewage discharge into the lake was favorable to plant growth. 

 It is likely that the availability of the nitrogen in this discharge was the main 

 determining factor. 



Appendix. 



The following pages contain a number of graphs which are of interest 

 only to those who are especially interested in the subject. The data from 

 which all of the graphs in the paper were made are included in this portion. 



For the sake of brevity various arl>itrary symbols were used in making 

 the graphs and in recording the data. The following key will render them 

 intelligible. 



Condition of the Sky — 



c — clear. 



d — dark, cloudy. 

 Condition of the surface of the Lake — 



m — calm, smooth, mirror. 



t — ripples. 



r — rough. 

 Temperature conditions — 



h— hot. 



w — warm. 



n — moderate. 



X — cool. 



z — cold. 

 Amount of Vegetation — 



vv — extremely dense. 



V — dense. 



a — abundant. 



s — sparce. 



o — none. 



