484 
1. Other things being equal, bodies of fresh water free 
from vegetation (submerged macro-flora) produce more plank- 
ton than those rich in such vegetation.* Thus, the amount of 
plankton produced (as indicated by the averages of all of our 
collections in the several localities examined) in our open 
waters is from two to eleven times as great as it is in our lakes 
closed by vegetation. As shown in the table on page 429, the 
average planktons in Thompson’s and Phelps lakes are 7.94 and 
and 19.65 em.’ per m.° respectively, while in Quiver and Dogfish 
lakes the quantity is only 1.70 and 4.22. Flag Lake, with an 
average of 11.46 cm.’, is an interesting exception to this con- 
trast which will be discussed in another connection. The con- 
trast is even more striking if the averages of the monthly 
averages for all the years are made the basis of comparison, as 
in the following table and diagram. 
COMPARISON OF PLANKTON PRODUCTION IN VEGETATION-POOR AND 
VEGETATION-RICH WATERS. 
Vegetation-poor Vegetation-rich 
Month D fi h Thompson’s|n,.1..7 3... Ratio 
Quiver Lake eee ie tee S!Phelps Lake 
Jantany 2 2cs cecens ease .27 -53 3-79 3.29 1:9 
Mebruany son cc cnscchren se .67 1.10 1.27 5.68 1:4 
March) sc 05 /jeletrasvew see -77 1.96 2.96 5.68 1:3 
AND TAL  eiata ok wraieisiets esti 7.26 10.50 14.49 11.77 1:1.5 
May 6.85 5-79 29.59 25.33 1:4 
PUNE earache ew icperok omer 1.25 1.75 10.66 II.40 1:7 
Jul yyeietae wes evarciareterets eye : -78 1.95 4.74 ~ 8.50 1:5 
AU PUSS Saack eemeneceee Shy) 2.51 6.19 58.12 1:20 
Seplembet pees snes aif 2.39 5-37 47.25 1:17 
October re sc. seein 69 3.05 10.64 27.68 1:10 
November.....-..-...:- -23 2.64 6.39 41.57 1:17 
Decemberest.n secon 63 3.76 3.08 _ 21 .96 1:6 
Gr’d av. of monthly av.. 1.75 3.16 8.26 22.35 1:6 
On this basis, the waters full of aquatic vegetation pro- 
duce throughout the whole year less plankton than waters 
free from such growths. Relatively few exceptions to this rela- 
* This relation of vegetation to the plankton may be formulated as follows: 
The amount of plankton produced by bodies of fresh water is, other things being 
equal, in some inverse ratio proportional to the amount of its gross aquatic vegeta- 
tion of the submerged sort. 
