282 



In his second memoir Angot (1886) studied the additional data 

 for the years 1882 and 1888. A new determination of the influence 

 of altitude on the epoch of leafing again gave an average retardation 

 of four days for each 100 meters of altitude for the lilac, the chest- 

 nut, the birch, and the oak. The average mean daily temperature 

 of the air at the date of leafing varies between 5° and 12° C. for the 

 lilac, with an average of 9.1° ; from 4° to 14° C., with an average of 

 10.1°, for the chestnut; from 7° to 15° C., with an average of 10.7°, 

 for the birch; from 5° to 16°, with an average of 11.3°, for the oak. 

 These ranges are so large that it is impossible to indicate any simple 

 relation between the leafing of these plants and the mean daily tem- 

 perature at this epoch. The mean of the daily maxima were also 

 computed for the epoch of leafing, and were 14.6° for the lilac, 15.7° 

 for the chestnut, 16.1° for the birch, and 16.4° for the oak. But 

 again the variations were too large to attach any phenological impor- 

 tance to these numbers. 



As to the sum total of temperatures Angot adopts, not a constant 

 date, as December 1 or January 1, but dates that are variable for each 

 station and each year and approximately represent the close of the 

 last period of freezing weather. They vary in this case between the 

 18th of January and the 13th of February. After laborious calcu- 

 lations by different methods and starting from different initial tem- 

 peratures he concludes that the leafing of the four plants under con- 

 sideration occurs when the sum of the mean daily temperatures, 

 counted from 0° C, or the sums of the maximum daily temperatures, 

 counting from 0° C. and beginning at the date of the commencement 

 of vegetable growth as above defined, attains the values given in the 

 following table : 



In order to decide which of these two modes of calculation, daily 

 mean or daily maxima, are most proper it will be necessary to oper- 

 ate upon a much longer series of observations. 



The flowering of the narcissus, the lilac, the chestnut, the elder, and 

 the linden was studied in a manner similar to that of the leafing. The 

 retardation for altitude is, as before, four days to the 100 meters. 

 The man daily temperature at the date of flowering is: For the nar- 

 cissus, 6° to 14° C, average 9.4° ; for the lilac, from 8° to 15° C, 



