264 



meteorological conditions must be accessible, samples of which I have 

 prepared for twenty United States stations." 



If we suppose some wheat to have been sown on the :l2d of Septem- 

 ber, 1871, near Paris, and if we adopt the rule established by Gas- 

 parin that the vitality of the seed is actively aroused as soon as its 

 temperature in a moist earth exceeds 5° C, and that it germinates 

 visibly when it has received a sum total of mean daily temperatures 

 that is equal to 85° C, and that the sprout rises above the surface of 

 the earth in a few davs after the seventh, then we obtain six days as 

 given in the folloAving table for the interval from sowing to germina- 

 tion. A similar computation for every other date of sowing, as given 

 in the following table, shows at a glance the effect of the temperature 

 of tJie soil on this phase of plant life. 



Duration, in (Itn/n. from aoiriiifi to f/rriiiiuation of irintrr irJieat at .l/o»f.«oj<r/.s, 

 France, for the i/ears 1872-1881. 



In studying the preceding table we recall that the duration of 

 germination varies slightly with the condition of the soil and the 

 depth of the grain below the surface; these two considerations will 

 be perfectly allowed for if we observe directly the temperature of 

 soil by a buried thermometer. Such observations are earnestly recom- 

 mended to all agricultural experiment stations, as they are, evidently, 

 more directly applicable to the growth of plants than any crude 



These tables are omitted in ttie present edition. 



