ANNUAL REPORT, 1941 41 



achusetts, under the terms of a memorandum of understanding drawn up with 

 that company. Several other lots of seedlings from crosses made at East Ware- 

 ham are set out in permanent locations on the State Bog where they will be al- 

 lowed to grow until final assessment of their worth for propagation can be made. 



Oxygen Content of Winter Flooding Water in Relation to Injury to Cranberry 

 Vines. (H. F. Bergman.) Studies of the effects on cranberry vines of a lack of 

 oxygen in the water during the winter flooding period were continued, in an 

 attempt to correlate various types of injury with known low contents of dis- 

 solved oxygen over approximately known periods and to obtain additional data 

 as to the conditions under which injury occurs. Three cylindrical sheet-iron tanks, 

 about 5 feet in diameter, were placed on the State Bog, one each on sections 

 panted with vines of Early Black, Howes, and McFarlin varieties. The bog 

 was flooded on December 5, 1940, and froze over within a few days and remained 

 frozen continuously until about the middle of March. Covers to exclude light 

 and thereby prevent the liberation of oxygen by photosynthesis were placed on 

 the tanks on January 18, 1941. 



The importance of photosynthesis in maintaining the dissolved-oxygen con- 

 tent of the water on a winter-flooded bog covered with ice is shown by the course 

 of this oxygen content outside and inside the tanks during the winter. The 

 amount of dissolved oxygen in the water outside the tanks on Howes, Early 

 Black, and McFarlin vines increased from 5.3, 6.4, and 6.8 cc. per liter, respec- 

 tively, on January 15 to 7.2, 7.9, and 8.3 cc. per liter, respectively, on January 

 24 as a result of photosynthesis in the cranberry vines. A heavy snowfall on 

 January 24 prevented photosynthesis by excluding light, while the consumption 

 of oxygen by respiration of the cranberry vines and of organisms which decom- 

 pose organic matter continued. As a result the dissolved oxygen in the water 

 outside the tanks decreased to less than 2 cc. per liter, although probably for not 

 more than 5 or 6 days. A heavy rain on February 7 removed most of the snow 

 and the remainder froze into the ice. Thereafter, the dissolved oxygen in the 

 water outside the tanks on Early Black and McFarlin vines increased rapidly, 

 and by February 12 it had come up nearly to the same content as on January 24. 

 The oxygen content of the water outside the tank on Howes vines remained near 

 2 cc. per liter until February 20 when it also began to increase. 



The dissolved oxygen in the water inside the tanks on January 15 varied from 

 4 to 5 cc. per liter. Because of the exclusion of light by the covers, little or no 

 photosynthesis could take place and the oxygen content of the water decreased 

 steadily. By January 24 and from then until February 27 there was no dis- 

 solved oxygen in the water inside the tank enclosing vines of the Howes variety, 

 and not more than 0.4 cc. per liter from February 27 until March 20. In tanks 

 enclosing the other two varieties of vines there was less than 1 cc. of oxygen per 

 liter of water for about a month from February 1 to March 1 except in the tank 

 on Early Black vines where the oxygen content of the water increased to slightly 

 more than 2 cc. per liter for a few days around February 12. On February 28 

 nine inches more water was pumped onto the bog which brought the oxygen 

 content of the water up to more than 2 cc. per liter. Thereafter, e.xcept for a few 

 days about March 13, there was never less than this amount of oxygen in the 

 water. Soon after March 20 the ice went off the bog and the dissolved-oxygen 

 content again increased. 



The water was taken off the bog on April 1, 1941, and the tanks were then 

 removed. Counts were made during the summer and autumn to ascertain the 

 average number of flowers and fruits per upright, the percentage of buas killed, 

 and the percentage of flowers that set fruit on vines of each of the three varieties 

 both inside and outside the tanks where the dissolved oxygen content of the water 



