267 
heading occur during the very cold season likely to be injurious to 
vegetation. 
We pass now to the period from the heading of the wheat to the 
flowering. According to the determination of Herve Mangon, the 
sum total of the mean daily air temperatures in the shade necessary 
to flowering is 1,500° C., counting from the date of sowing, or 860° 
if counted from the date of heading. If we consider the date thus 
fixed for the flowering we shall find that it corresponds to a mean 
daily temperature at that epoch of 16.5° C. on the average of many 
years; but if we consider the individual years we shall find the actual 
mean temperatures of that date to vary from 8° to 22° C., and also 
that for temperatures below 13° the flowering becomes uncertain, 
prolonged, and detrimental to the crop; but as to the upper limit, 
92° C., there is no evidence that even higher temperatures will be 
injurious. The following table gives the calculated number of days 
that elapse from the sowing to the flowering, together with the aver- 
age duration and the corresponding average date. The correspond- 
ing tables of mean temperatures and lowest temperatures at the date 
and the quantity of rainfall are omitted for want of space. 
Duration in days from the sowing to the flowering of winter wheat at Mont- 
souris, France. 
| | | | | | Average for 
| | | | | | 1872-1881. 
Date of sowing. | 1872.| 1873.) 1874.| 1875.| 1876.| 1877.) 1878.| 1879.| 1880. | 1881. | 1882. | 
| | | (Ber| Date 
September 22-..| 244] 228 | 239) 237 | 2388] 208 | 231) 261} 242 | 2385] 239) 236 | May 16 
September 29_--| 243 | 226 | 237 | 238) 242 | 209 229 259 239 | 235 | 239 | 236 | May 23 
October 6 _.._.-- | 242] 220 287 | 238 | 243] 214 | 227| 258| 238} 233 | 235 | 235) May 20 
October 13 _..--- 241 | 225 | 234 | 284] 240] 217 | 222] 251 | 236] 231 | 232] 233 | June 3 
October 20 _.-..- 238 | 225 | 231 | 231] 237] 219| 216| 249| 234| 229/ 225] 231 | June 8 
October 27 ....-- 232 | 222| 226| 226) 232] 215/ 210| 249| 232] 224 | 222] 227 | June lz 
November 3..... 228] 219 | 220] 220| 227] 212| 217 | 245| 227} 219/| 215] 223/ June 14 
November 10...| 221| 217 | 218| 218 | 223) 206| 215| 238] 223/| 214| 214] 219| June 17 
November 17... 214] 211 212 | 212) 219] 203/ 209) 281) 217) 211) 212| 214 | June 19 
November 24 ...| 207 | 207 | 208| 208| 213] 198) 206 | 224| 211 | 205 | 208) 209 | June 2l 
December 1_-__-- 200} 203; 202) 202) 206] 191 202 | 218 | 204) 199| 202) 203) June 22 
December 8_-_-- 193 | 200} 195| 195) 199] 188| 197) 211 | 197| 195) 196| 197} June 23 
December 15....| 186 / 194) 188] 188 | 192 | 184 | 190) 204] 190) 191 | 189 / 191 | June 24 
December 22....| 179 | 189} 181| 181 | 186] 177] 183] 197 | 183] 186| 183] 184 | June 24 
December 29....| 172| 185 | 178| 178| 180] 171| 176| 191| 176 | 181 | 176 | 179 | June 26 
The ripening of wheat is perfected when the plant has received a 
sum total of mean daily air temperatures in the shade of 815° C. since 
the date of flowering. This result happens on the average of Paris 
forty-four days after flawering, and the individual irregularities 
searcely ever exceed four or five days. Therefore the date of flower- 
