APPENDIX 



187 



Table 6. The maximum, the minimum, and the mean amounts of 

 organic matter in the net plankton of Lake Mendota for the different 

 years are shown in this table. The results for 1914 and 1917 do not 

 cover full years; in the former instance the observations extended only 

 to the first of July and in the latter to the first of June. The results 

 are stated in milligrams of organic matter per cubic meter of water. 





Year 



Number of 

 Samples 



Maximum 



Minimum 



Mean 



1911 



22 



464 



42 



175 



1912 



29 



1,055 



84 



393 



1913 



35 



697 



87 



373 



1914 



14 



426 



99 



289 



1915 



34 



810 



113 



367 



1916 



39 



1,135 



73 



343 



1917 



11 



866 



92 



271 



Table 7. The variations in the percentage of nitrogen in the net 

 plankton and the mean percentage for the different years are indicated 

 in this table. Nitrogen determinations were not made on all of the sam- 

 ples collected in 1916 and 1917. The mean annual percentages are 

 based on the mean quantity of nitrogen and the mean quantity of or- 

 ganic matter in the samples on which nitrogen determinations were 

 made. In the first part of the table the percentages of total nitrogen 

 are indicated, but in the second part the percentages do not include 

 the nitrogen of the chitinous shells of the Crustacea. 



Year 



Number 



of 

 Anafyses 



Per Cent of Sample 



Per Cent, Ash Fre3 



Maximum 



Minimum 



Maximum 



Minimum 



Mean 



1911 

 1912 

 1913 

 1914 

 1915 

 1916 

 1917 



22 

 29 

 35 

 14 

 34 

 26 

 6 



8.33 

 8.9^ 

 9.22 

 9.96 

 8.11 

 7.02 

 9.97 



3.92 

 4.47 

 4.16 

 6.60 

 4.59 

 3.95 

 5.76 



9.44 

 9.55 

 11.20 

 11.10 

 10.72 

 9.00 

 11.11 



5.75 

 5.61 

 6.26 

 6.95 

 7.22 

 5.50 

 8.43 



7.93 

 8.11 

 8.14 

 8.65 

 8.87 

 8.16 

 10.21 



