PAPERS OX BIOLOGY AND AGRICULTURE 159 



made year after year convey a very definite impression 

 of wide seasonal differences in behavior of varieties and 

 individuals; of very unequal response to exterior condi- 

 tions observed and assumed to exert influence either as 

 stimuli to increased activity, or as agents operating to 

 retard or diminish plant processes and, further, of the 

 fact that factors governing performance are complex and 

 dependent upon physiological changes that are difficult to 

 understand or rightly interpret. 



Amount of bloom is not determined at blooming time, 

 but during the preceding year at the time of bud forma- 

 tion and, whether the amount is large or small, must de- 

 pend upon the condition of the trees and the conditions 

 to which they are subjected during the bud forming per- 

 iod. 



Classified as belonging to one or the other of two di- 

 visions, no bloom or not sufficient for a crop and enough 

 for a crop, the 1696 records for the 106 varieties for 16 

 years divide as 636 with none or insufficient bloom and 

 1060 with sufficient for a crop. From examination of the 

 records it appears that 1913 was the year of maximum 

 performance, for in that year 101 or 95.29 percent of the 

 varieties had sufficient bloom ; next to this was 1915 with 

 97 or 91.51 percent with satisfactory bloom. At the other 

 extreme, 1902 and 1907 had each only 41 or 38.68 percent 

 of the varieties having sufficient bloom. In other years 

 the distribution was irregular. 



Very heavy or excessive bloom occurred 92 times on 58 

 varieties in 8 of the 16 years ; 32 varieties appear in the 

 list recording very heavy bloom but once ; 21 varieties ap- 

 pear twice; 3 appear 3 times; one, 4 and another 5 

 times. For the 21 varieties each appearing twice, there 

 were two cases in which the years of heavy bloom were 

 consecutive, five cases of alternation with sufficient bloom 

 in the intervening year and 14 cases in which the years 

 of heavy bloom were separated by from 8 to 12 years. 



The variety having very full bloom in 4 years was Old- 

 enburg; the years were 1902 and 1904, and 1914 and 1916 ; 

 between each of these pairs was a year of moderate 

 bloom and for the 16 years the variety has record of 12 

 good and 4 poor years. 



