RELATION OF ALGAE TO DISSOLVED GASES. 191 
The above figures and the interpretation of them agrees, 
in the main, with those of Morren (’41) already mentioned. 
His were given for every day for the entire year. It is hoped 
that an extension of the above data may serve to confirm the 
interpretations and conclusions already reached. The later 
dates are less significant. The “bloom” disappeared with the 
frost of early November, and there was a decrease in the 
oxygen content of the water, reaching a minimum again 
November 21, when the lagoon was almost clear of vegetation. 
This, with the autumn rains bringing in drainage water, 
kept the oxygen figure down, while the alkalinity gives place 
to neutrality for a time, to be followed by an increasing 
amount of free COz, reaching a maximum in December. The 
GRAPH I. 
10 : 10 
8 h ss Ae --| 8 
6 ‘\ ex ened EN |e N u 6 
NEw AN /[LN \ 
4 ~~ i A 4 
114 0 
‘, i \a —-Fe-tn 
2 < ‘ 2 
4 : \e 4 
ee ee { ! Vv 
6 <H 6 
+I 
8 8 
10 10 
yune |  vury | auaust |septemser| octosen | NovemBeR| DEC. 
Graph showing the amount of 02 (——) and C09 (----) ince per liter. 
decay of organic matter washed from the dead leaves of a late 
autumn and the gradually decaying green alge, together 
with the decay of the blue-greens of the water-bloom, would 
materially increase the amount of COz and consume the 
