24 MASS. EXPERIMENT STATION BULLETIN 293 



Average 

 Average Temperature F difference 

 between 

 Plot Plot Unwatered watered and 



watered Watered check unwatered 

 Date Weather Conditions Hour July 20 July 23 °F 



July 25 Clear, strong breeze 2 p. m. 92.25 92.38 96.91 4.59 



July 26 Clear, strong breeze 12:30 p.m. 89.25 88.43 92.1 3.26 



The general average difference in temperature between the watered and un- 

 watered plots for five days (excluding one cloudy day when practically no differ- 

 ence occurred) was 3.08° F. Readings taken at different times of day indicated, 

 as would be expected, that the greatest difference occurred in the early afternoon, 

 i. e., during the warmest part of the day. It is interesting to note that even six 

 days after water was applied to the first plot, the difference in temperature, in 

 comparison with the unwatered bog, was as great as during the first day after 

 application. 



During the period when the berries were setting, considerable injury to the crop 

 occurred on many bogs, for many flowers turned brown and dry and, of course, 

 did not set fruit. Drought conditions caused most bogs to be unusually dry during 

 the blooming season. The critical temperature above which cranberry flowers 

 are injured is not known; but in view of the effect which watering has on the air 

 temperature above and near the surface of a bog, as shown by the experiments just 

 outlined, it seems probable that had the bogs been as moist as in normal seasons, 

 the temperature might in many cases have remained below the point where injury 

 occurs. How much this reduction of temperature is due to transpiration from the 

 cranberry plants and how much to direct evaporation from the bog, it is impossible 

 to say. Both these factors, however, depend more or less on the supply of mois- 

 ture in the surface soil of the bog. 



Cranberry Pollen Studies. (W. H. Sawyer.) Through a detailed study of 

 the cranberry flower and pollination, several interesting facts have been developed. 



Even during hot, dry weather, if pollination does not occur, the stigma remains 

 moist and receptive for pollen for seven days, and under more favorable conditions 

 of coolness and moisture, it is evident that pollination can take place for a con- 

 siderably longer period. This is very significant on its influence in insuring a set. 

 Also pollen must be thoroughly ripe before it is capable of germination, and such 

 pollen is found only in anthers that have begun to shrink and turn brown. 



When pollen is ripe it is shed from the anthers upon the slightest disturbance. 

 A little pollen may be shed when the flower first opens, but maximum liberation 

 takes place a few hours before the style has elongated enough to bring the stigma 

 even with the anther tips. This occurs from twenty-four to thirty-six hours after 

 the flower has opened. 



The shape of the flower and the arrangement of the stigma and anthers are such 

 as to supply reasonable justification for a lack of self-pollination. Distilled 

 water was found to be as satisfactory as any other medium tried for the germina- 

 tion of cranberry pollen, but the pollen tubes did not grow very satisfactorily 

 after germination. A 1 per cent solution of cane sugar was found to be the best 

 medium for all purposes, and the best results were obtained when the pollen 

 floated on the surface of the solution. 



The range of temperature for pollen germination under laboratory conditions 

 was 29°C.; with a minimum of 8°,the optimum from 28°to 32°, and a maximum of 

 37°. Within the temperature range where germination was possible, the per- 

 centage of germination remained constant, but there were variations in the time 

 required, and these differences were also influenced by the variety. 



