2r)5 



approximations derived from the observation of the temperatii''e of 

 the air only. If when the grain has sprouted the soil continues very 

 dry, the nourishment having all been drawn from the seed, the young 

 plant may droop and die. If, again, the frost jjenetrates to the seed 

 while it is germinating, many of the seeds will perish, and the field 

 will appear as if sparsely sown, but this latter mishap is generally 

 repaired by nature if the soil is good and the springtime favorable, 

 for the sowing is generally in excess and the extra heading will 

 supply the loss of the seeds that have perished, but in poor soil the 

 harvest will be notably diminished, and often it will be i)rofitable to 

 plow the soil for a neAV sowing. 



In any case the chances for a successful crop xarj very much with 

 the date of the sowing, as we shall see by the study of the following 

 table, which shows that in each year the season for sowing that is 

 favorable to the crop of that j^ear is very much restricted by the early 

 arrival of the winter cold. Thus in 1871 the sowing Avas stopped on 

 the '20th of October by the cold weather ; in 1872 it continued through- 

 out the autuuni until the 20th of December; in 1880 it occurred on the 

 8d of November. Sometimes heavy rains prevent the sowing, but in 

 1881 neither cold nor rain prevented field work until the middle of 

 December. [In order to save space I have omitted the elaborate 

 tables of frosts, low temperatures, and rains given by Marie-Davy for 

 each of these years and weeks. — C. A.] 



The grain now arrives at the epoch of heading, at which the orig- 

 inal stalk becomes several branches, each of which bears an immature 

 head on which the rudimentary seed can already be counted under 

 the microscope; the number of such seeds will not increase in the 

 further development of the plant, but many of them may not come to 

 maturity; therefore a careful count of these rudimentary seeds over 

 a small area of the field would give a first estimate of the maximum 

 possible crop. 



According to Gasparin the length of time that elapses from the 

 moment when the mean daily temperature of the air in the shade is 

 5° C. up to the date of heading of the wheat is such that the sum 

 total of the mean daily shade temperatures is 430° C, but as the 

 initial date is difhcnlt to determine we shall in our calculations adopt 

 the rule of }Ter\'e Maugon, according to whom the sum of the mean 

 daily temperature in the shade, rejecting all that are below (5° C 

 (at which the wheat does not yegetate), is (140° C. if we count from 

 the date of sowing, or 5.55° C. if we count from the date of germina- 

 tion. The following table is computed by counting from the former 

 date; a parallel computation from the latter date shows that on the 



