272 



The preceding table shows that the only important difference 

 between these good and poor years consists in the fact that the latter 

 have more rain and less sunshine. The influence of the tempera- 

 ture of the air as such and of the number of days of freezing weather 

 does not seem to be important, so that we must conclude that the 

 cloudy weather which accompanies the rain and cuts off the sunshine, 

 affects the plant unfavorably only by this loss of radiation. xV defi- 

 ciency of light is more unfavorable than excessive moisture in the 

 soil. In general in France, and especially in dry countries such as the 

 arid regions of America, it is the deficiency of Avater in the soil that 

 affects the crops unfavorably. Where an abundance of sunshine 

 exists the wheat plant can utilize more water than ordinary soils 

 possess; hence the great advantage of irrigation, as long since prac- 

 ticed in Mesopotamia, Egypt, China, India, Arizona, and South 

 Africa. The numerical data with regard to the quantity of water 

 and the times of irrigation have been approximately determined at 

 agricultural experiment stations, Avitli results given in the next sec- 

 tion of this present report. 



In the Annuaire for 1890 Marie-Davy gives climatic tables espe- 

 cially adapted for phenological study. 



In order that meteorological data may he presented in form con- 

 venient for the comparison of crop reports or for the prediction of 

 the future development of the current crop or for other studies in 

 the growth of plants it is necessary that the data should be compiled 

 in a manner very different from that ordinarily given in climato- 

 logical tables. The monthly means and other data given in the 

 so-called international form recommended and urged by the recent 

 international conferences of Europe have much more regard to 

 dynamic meteorology and to questions in hygiene than to questions 

 in agriculture. For our agricultural studies a continuous sunnna- 

 tion must be made from the beginning to the end of the year, either 

 by decades, by weeks, by pentads, or even by days for each succes- 

 sive year. From such tables we can calculate the total work that 

 has been done upon the plant bj the sunshine and the work that 

 remains to be done before the harvest. Such tables can be compiled 

 in an empirical approximate way from the data furnished by the 

 international forms, as I have attempted to do in table — ." But it 

 is far better to prepare them from the original records, and they 

 nuist be prepared for every agricultural experiment station in the 

 United States before we can profitably study the influences of our 



a Tliis table is omitted iu the present edition. 



