WEATHER IN CRANBERRY CULTURE 17 



The effect of oxygen given off in photosynthesis on the dissolved oxygen con- 

 tent of the water is shown also by the great increase from February 4 to 12. 

 Whether or not the oxygen content of the water changed between February 4 

 and 7 is not known. The intensity of the incident radiation throughout most of 

 the daylight period on February 5 and 6 was much greater than on February 2,3, 

 and 4; but since most of the snow on the ice on February 4 remained until Feb- 

 ruary 7, very little, if any, of the incident light may have reached the vines. Much 

 of the snow on the ice was melted by a rainfall of 1.49 inches on February 7 and 

 the unmelted snow afterward froze into the ice. The ice was thinner also. The 

 intensity and duration of the incident radiation on all days from February 8 to 

 11 was as great, and on February 12 nearly as great, as on January 20 and 21, 

 the two days among those between January 15 and 24 on which it was greatest. 

 Because of this and because of the disappearance of the snow and some reduction 

 in the thickness of the ice, more light reached the vines, causing increased photo- 

 synthesis with a resulting increase in the oxygen content of the water. 



The dissolved oxygen content at station 1 was lower than at stations 2 and 3 

 from February 12 to March 13 because the ice was thicker and had more snow 

 included in it at station 1 than at the other stations. The difference in thickness 

 was only about 1 inch on February 12 but increased to 3 to 3.5 inches on February 

 27 when the ice was 7.5 inches thick at station 1. The difference in thickness 

 thereafter decreased, but on March 13 the ice was still 1.5 inches thicker at station 

 1 than at the other stations. Therefore, the vines at station 1 received light of 

 lower intensity than those at the other stations with a corresponding reduction 

 in the amount of oxygen given off in photosynthesis. 



The dissolved oxygen content of the water at stations 2 and 3 was lower on 

 February 13 than on February 12 for the following reasons. The dissolved oxygen 

 content of the water decreased during the night of February 12 because of the 

 ox3gen used in respiration. The incident radiation during the forenoon of Feb- 

 ruary 13 was of low intensity because of cloudiness; it increased from zero to 12 

 per cent of the June 21 mean maximum during the first two hours of the day and 

 during the next two hours varied from 10 to 14 per cent. With light of this 

 intensity, enough may have passed through the 4.5 inches of ice then on the bog 

 to cause photosynthesis to go on slowly, but the amount of oxygen given off was 

 not sufificient to make up for that used in respiration during the preceding night 

 and part of the forenoon. 



Conditions evidently were favorable for photosynthesis during at least most 

 of the period from February 13 to 27 since the oxygen content of the water at 

 stations 2 and 3 increased during this time. However, these conditions need not 

 be discussed since other examples have been cited to show the relation between 

 the amount of oxygen given off in photosynthesis and the intensity of the light 

 received by the cranberry vines and further discussion could add nothing new. 



More water was pumped onto the bog on February 28, increasing the depth by 

 about nine inches. The pond water used for flooding had a high dissolved oxygen 

 content and probably brought that of the water at all stations nearly, if not fully, 

 up to its saturation capacity. 



The ice went off the State Bog, except around station 1, immediately after 

 March 13, but the bog froze over again on March 17-18. The few days during 

 which the water was in contact with the air brought its dissolved oxygen content 

 nearly, if not fully, up to its saturation capacity at all three stations, although 3.5 

 inches of ice remained over a small area around station 1. 



