176 



From the data given by Mangon, ]SIarie-Davy deduces some further 

 phenological constants ^Yhich will be useful, viz, for winter wheat 

 in Normandy, the sum of the daily temperatures in the shade, reject- 

 ing all below" 6° C., from sow^ing to germination is 85° C. ; from ger- 

 mination to heading, 555° C. ; from heading to maturity, 1,810° C. 

 This gives from sowing to heading G10° C, Avhereas Gasparin, fol- 

 lowing his owni rule, which takes the sum of all temperatures after 

 the date at which the temperature of 5° C. is attained, finds 430° 

 for this constant. 



Wheat begins to grow visibly whpn the mean daily temperature is 

 about 6° C. This mean daily temperature is attained on the average 

 of many years on the dates given in the second column of the fol- 

 lowing table. (See Marie-Davy, 1881 and 1882, p. 184.) The aver- 

 age dates of harvest are given in the third column; the interval or 

 growing period in the fourth column; the fifth column contains the 

 sums of the mean daily temperatures of the air in the shade (after 

 the date on which a mean temperature of 6° was attained), the sixth 

 column gives the sums of the mean daily temperatures of the 

 thermometer in the full sunshine, as determined by Gasparin. The 

 close agreement of the two latter numbers is considered by Marie- 

 Davy an argument in favor of the idea that temperatures in the sun- 

 shine are better than those in the shade as a measure of the influence 

 of heat and light on the growth of plants. 



Balland (see Marie-Davy, 1881, p. 186) has made a perfectly simi- 

 lar computation with reference to the ripening of wheat cultivated on 

 a large scale at Orleansville, in Algeria, with the following results: 



1878 2, 498 



1879 2,433 



Average 2,462 



The results of Mangon, Balland, and Gasparin agree so closel}^ that 

 a strong argument seems to be afforded in favor of using the ther- 

 mometer ex^30sed to the full sunshine. The differences in their results 

 are quite comparable to the differences found by Vilmorin to exist 

 between different varieties of the same seed. 



The values of the thermometric constants, as computed by Herve 

 Mangon's method, for other grains cultivated in Normandy are given 



