PLANKTON PRODUCTION IN FISH PONDS 
151 
phosphorus is the limiting factor, for at no time was it completely exhausted. More- 
over, the accumulation of a very considerable amount of soluble phosphorus was not 
followed by a correspondingly large increase in the organic matter. 
Table 5 shows that the dissolved phosphorus was, as a rule, rather low in C 4. 
Several times it was present only in traces. At other times it was absent altogether. 
The maximum of 0.012 p. p. m. occurred on August 20 and is correlated with a slight 
decrease in organic matter. The organic phosphorus varied from a minimum of 
0.015 p. p. m. on July 19 to a maximum of 0.058 p. p. m. on July 30 and on August 9. 
The variations in the dissolved phosphorus and the organic phosphorus are shown 
in Figure 3. 
ORGANIC MATTER 
The data on the organic matter in the centrifuge plankton are given in Table 4. 
This table shows that the organic matter in C 1 varied from a minimum of 1.35 
milligrams per liter on July 19 to a maximum of 14.43 milligrams per liter of water on 
109553—30 3 
