156 ILLINOIS STATE ACADEMY OF SCIENCE 



ly low temperatures, by excessive rainfall, or by rapidly 

 alternating periods of heat and cold so that flowering is 

 very irregular and the blooming period much prolonged. 



Of the 106 varieties, 38 are recorded as having bloomed 

 in each of the 16 years ; 24 bloomed in each of 15 years ; 

 23 in each of 14 years ; 11 in each of 13 years ; 5 in each of 

 12 years ; 3 in each of 11 years, and 2 in each of 10 years. 

 For the 16 years (1901-1916), flowering periods have 

 ranged from 10 to 22 days ; the average is approximately 

 16 days. Records of 1906 and 1911 are very near the 

 average ; seven years had periods one to six days longer 

 than the average and seven years had periods one to six 

 days shorter than the average. 



The full flowering period for the 16 years is included 

 between the dates April 2 and May 21 -and is thus 50 days 

 in length, but this includes one year so abnormal as to set 

 it apart from all other years; I refer to 1910, in which 

 year flowering began April 2 and ended April 19. Omit 

 1910 and the full flowering period has extended from 

 April 18 to May 21, or 34 days. 



Some varieties tend to bloom early, others late, but 

 there is no variety holding place as earliest bloomer or as 

 latest bloomer with constancy ; they vary within wide lim- 

 its. Causes for these variations must be looked for in 

 seasonal differences in vigor of individual trees. All 

 trees are subjected to the same atmospheric conditions 

 and presumably the soil is uniform, but all trees do not 

 behave in the same manner with reference to their func- 

 tions; one tree, in a given year, makes greater growth 

 than another, has more and better foliage and exceeds its 

 neighbor in fruit production; in another year the per- 

 formance of the two may be exactly reversed in all these 

 particulars. In the same way response of flower buds to 

 the stimulus of advancing spring may be quick and vigor- 

 ous or tardy and weak, depending upon the condition of 

 the individual. 



The seasonal abnormality of 1910 was so great that it 

 deserves brief mention. The bloom extended from April 

 2 to 19, a period of 18 days. A period of the same length 

 was recorded for 1909, one a day shorter in 1904, another 

 a day longer in 1905 : nine of the 12 remaining years had 



