EFFECT OF TEMPERATUKE. 27 



Mangos were nearly as active as peaches. The citrus fruits were 

 exceedingly inactive. 



No satisfactory theory based on the composition or size of fruits 

 has been found to account for the differences in the respiratory 

 activity. A few moments' inspection shows that the rate of respira- 

 tion is not a direct function of content of sugar or of acid, and does 

 not depend upon size, as Japanese persimmons are richer in sugar 

 than strawberries, yet are less active; oranges and lemons, which 

 differ greatly in acid content, have about the same respiratory activity; 

 red currants differ greatly in respiratory activity from black currants, 

 although they are nearly the same in size. Generally speaking, the 

 fruits which have a short growing period, mature rapidly, and become 

 over-ripe quickly — as strawberries, raspberries, and blackberries — 

 are very active physiologically. At the other extreme are the slowly 

 developing citrus fruits, which are very inactive. Intermediate in 

 these respects are the other fruits. Peaches have a shorter life his- 

 tory than apples and are more active. Summer apples do not keep 

 so well as winter apples, and respire more rapidly. 



In the case of 29 series of determinations the values at the cold- 

 storage temperatures fall below the empirically drawn lines, and it is 

 therefore probable that in cold storage most fruits respire less actively 

 than would be calculated from equation 1, page 20. In 11 out of 15 

 determinations the value at the incubator temperatures falls below 

 the line, and it is probable that where this occurred the rate of res- 

 piration declined during the period of observation. In general, how- 

 ever, the respective respiratory activities are well denned by equation 

 1, in which log y , determined experimentally as described on page 20, 

 is the constant characteristic for each kind of fruit and in which the 

 constant a is nearly constant for all fruits, varying slightly from one 

 fruit to another. 



In calculating the standard deviation and the probable error of the 

 constant a from the mean value 0.0376, formulas given by Daven- 

 port and Eietz x haVe been used. The standard deviation equals 



v 



ID 2 

 -^=0.00457, 



where ID 2 is the sum of the squares o* the differences from the arith- 

 metical mean, and N is the number of observations. The probable 

 error, 



±E= ± Standardisation xa6745= ^^ 



" determines the degree of confidence we may have in using the 

 mean as the best representative value of a series of observations. 7 ' 2 



1 Univ. of Illinois, Agri. Exp. Sta. Bui. 119, 1907. 



2 Mellor, Higher Mathematics for Students of Chemistry and Physics, 1905, p. 514. 



