280 



A similar elaborate study of the harvest of rye gave the following 

 results : 



(1) Retardation for altitude is approximately four days per 100 

 meters, with some indication that the correct figure is rather less 

 than this. 



(2) The date of harvest reduced to sea level begins with the 5th of 

 June in southern France and ends with the 25th of July on the 

 northern border. 



(3) The sum total of temperatures computed by the three methods 

 A, B, C, above mentioned, shows that whatever method be finally 

 adopted as the best, these sums are less for rye than for winter wheat. 



A similar study for spring barley shows the following results: 



(1) A retardation of four days per 100 meters of altitude suf- 

 ficiently harmonizes the observations. 



(2) A retardation of thirty or forty days in the date of sowing 

 has no appreciable effect on the date of harvest, which varies from 

 the 20th of June in southern France to the 14th of August on the 

 northern boundary. 



(3) The sum total of temperatures from sowing to harvest is too 

 variable to be determined. 



A similar study of the flowering of the narcissus {Narcissus 

 fseudonarcissus) shows that the retardation of the date of flowering 

 is at the rate of four to five days per 100 meters, and four days can be 

 adopted without notable error. 



A study of the currant {Rihes ruhrum) shows that the retarda- 

 tion is between three and four days per 100 meters. The sum total 

 of heat from December 1 up to the date of flowering, as deduced by 

 the second and third methods, but under three different assumptions — 

 i. e., that the initial temperature is 4°, 6°, 8°, respectively, seems to 

 show that 4 is the proper figure for this plant. 



A study of the flowering of the lilac shows that a retardation of 

 four days per 100 meters best satisfies the observations of both leafing 

 and flowering. The latter begins in southern France on the 22d of 

 March and ends in northern and eastern France on the Oth of May. 

 The calculation of the heat required for leafing shows that the most 

 accordant results are obtained when we take the sum of maximum 

 daily temperatures above 4° C. and count from the date of the last 

 heavy frost, w^hich sum is about 360° C. For the flowering, on the 

 contrary, we have to take the sums of the mean daily temperatures, 

 counting from 4° C. and from the same date of frost, which sum is 

 then 350° C, while the sum of the maximum daily temperatures 

 would have given 695° C. 



A study of the leafing and flowering of the horse-chestnut (.^s- 

 eulus hippocastanvm) shows that the retardation of four days per 100 

 meters also satisfies these observations. The dates of leafing, as 



