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that the temperatures useful to the plant vary with the species and 
are decidedly above freezing, therefore students have taken other 
limits. Thus Gasparin and Hervé Mangon adopt 6° C. for the 
initial temperature in the growth of wheat. In order to ascertain 
the preper method of counting temperatures Angot has accomplished 
the labor of prosecuting three parallel computations by three different 
methods, as follows: 
(A) First method.—By observations of daily maximum and mini- 
mum temperatures. In this method Angot has examined separately the 
observed maxima and minima of the thermometer in the shade. After 
rejecting all observations below 6° C., he subtracts 6° C. from all the 
others and takes the separate sums of the remaining maxima and 
minima for each month and then the average of these two sums, 
which consequently represents a sum total of heat received during 
the month in excess of 6° C. 
(B) Second method.—By the daily means. In this method the 
mean of each day is first computed by taking the average of the 
maximum and minimum; 6° ©. is then subtracted from each of 
these daily means and all negative remainders are rejected. The 
sum of the positive remainders represents the sum total of heat 
received in excess of 6° C. 
(C) Third method—By maximum temperatures alone. In this 
method, which is a modification of that proposed by Hoffmann, a max- 
imum thermometer is exposed to the direct rays of the sun and the 
sum total of the maximum temperatures is used by Hoffmann. But 
Angot prefers to use the maximum thermometer in the shade, as in 
the first method, and, as before, takes the sum total of all the posi- 
tive remainders after subtracting 6° C. 
In all these methods the principal difficulty is to fix the epoch 
from which the summation should begin. Sometimes the date of 
sowing has been adopted as this epoch, but from the date of sowing 
up to the date of sprouting the seed and the young plant are sub- 
jected only to the temperature of the soil, and not to that of the air, 
which often differ considerably. It would perhaps be better to 
start with the date at which the plant appears above the earth, but 
the date of sprouting is not generally given by observers. He there- 
fore provisionally adopts the 1st of December as the point of depar- 
ture and calculates the sum total of temperatures for the nine stations 
in France for which the dates of flowering and harvesting of winter 
wheat have been best determined for the years 1880 and 1881. The 
agreement among themselves of the numbers calculated by these 
three methods for nine stations and two different years is such that 
no decision can be arrived at as to which method*is the best, and 
such decision is reserved for a future study of other harvests. 
