A STUDY OF VARIATION IN APPLES. 29 



Form. 



The main purpose of this work has been the study of the variation 

 in form of the apples and the causes thereof. The continuation of our 

 observation has resulted in the accumulation of data that confirm earlier 

 conclusions' and afford basis for some further deductions concerning the 

 problem. 



Ben Davis tree No. 7 which has borne the largest apples has also borne 

 the most flattened of any, while the most elongated have been from 

 tree No. 8 closely followed by tree No. 2. The mean indexes of form 

 from 3'ear to j^ear have also been fairly consistent, No. 7 ranking first 

 four times, second once and fourth once during the six years. The other 

 trees have been more variable, but trees Nos. 2 and 8 have shown a tend- 

 ency toward elongation. As with size the differences in form are more 

 constant in the different parts of the trees than with the different trees. 

 The upper south apples have been the most flattened every year, but those 

 of trees Nos. 1 and 3 from the lower north portions have been the most 

 elongated four years out of six. The other two portions of the trees have 

 been more variable, but the lower souths have been slightly the more 

 flattened. As regards the standard deviation and the coefficient of varia- 

 biUty, they do not seem to have any significance whatever; such small 

 differences as occur are probably wholly chance fluctuations. 



Turning now to the discussion of the difference in form from year to 

 year and its relation to air temperature, which has been the main object 

 of inquiry, we find that the paralellism between the variation and the 

 temperature for a period following blossoming previously observed has 

 been maintained in succeeding years. This relationship is shown in Fig. 1, 

 which shows the fluctuations in mean daily temperature for twenty-five 

 days following full bloom. This shows that a low temperature following 

 blossoming is always followed by a low coeflScient of form, i.e., relatively 

 elongated apple. The past season of 1913 has been the coolest of any 

 for nearly the whole period of twenty-five days, and the apples have 

 been the most elongated, while in 1908, 1911 and 1912, in which this 

 period was relatively warm, the coefficient of form is much larger, i.e., 

 the apples are more flattened. In the other years both the temperatures 

 and coefiicients of form have been intermediate. 



The curves of temperature, not only for the period shown in the diagram 

 but for the entire growing season as well, have been carefully scrutinized to 

 ascertain the critical period which determines the form of the apple. 

 Consideration has also been given to other factors of climate, such as rain- 

 fall, humidity and sunshine, — whether they may have an effect. As a 

 result of this inquiry there appears no evidence that factors other than 

 that of temperature for a part or all of the twenty-five-day period have 

 any influence. Within this period the temperature from the sixth to 



1 Mass. Expt. Station Kept.: 23, Pt. I. (1911), p. 199. 



