PAPERS OX BIOLOGY AND AGRICULTURE 157 



periods from 2 to 8 days shorter and for three years the 

 periods were three and four days longer. Individual 

 periods ranged from 4 to 9 days much as in normal years. 

 It appears that the whole flowering period was simply 

 moved forward until the ending of bloom for the latest 

 flowering variety overlapped, by but one day, the earliest 

 opening of flowers in any other year. 



The early bloom is directly attributable to abnormal 

 weather in March. The month was dry, the rainfall only 

 .38 inch; mean maximum temperature 63°, mean mini- 

 mum 37.7°, and mean daily 52.3 \ For the last half of the 

 month the absolute maximum was 85°, the mean maxi- 

 mum 73.9% and mean minimum 44.7 : . For the period of 

 bloom, April 2-19, the mean daily temperature was 53.4°, 

 the mean maximum 65.6% and the mean minimum 42.1°. 



I wish now to compare this earliest blooming period of 

 1910 with the period for 1904 which was the latest record- 

 ed — May 5-21. The comparison covers 102 varieties that 

 bloomed in both years. The full flowering periods for 

 the two years differ but by one day, 17 days in 1904 and 

 18 days in 1910, but the beginning date in 1910 was 34 

 days in advance of the beginning date in 1904. 



Flowering periods for individual varieties tend to con- 

 centration about the 6, 7, and 8 day periods in both years : 

 the day-groups in 1904 number 8 with a range of from 4 

 to 14 days : in 1910 there were 6 day-groups with a range 

 of from 4 to 9 days. The average period was 7.34 days 

 in 1904 and 6.78 days in 1910, a half day longer (.56) in 

 the year when the blooming period occurred 34 calendar 

 days later than in the year of early bloom. 



It would be reasonable to expect that in contrasting 

 the blooming periods of two years, one of which was more 

 than a month later in the season than the other, the per- 

 iods of individual varieties would be shorter and con- 

 centrated under a less number of day-periods in that 

 year in which the blooming period was latest in season, 

 because the more powerful action of the sun and the pre- 

 sumed greater aggregate of heat units in the advanced 

 season would so stimulate plant functions that blooming 

 of varieties would proceed rapidly and result in concen- 

 tration within narrow time limits of short individual 



