251 



wine this year should have had a great simihirity with 1874. Never- 

 thelss, the Aviiie of 187H was not of very g-ood quality, which can 

 perhaps be attributed to a too prolonged growth of the vine stems, 

 caused by the humidity of the soil. If in general a good wheat year 

 corresponds Avith a good wine year this rule is far from invariable. 

 In regard to quality the vintage depends but too often on the late 

 spring frosts. 



The extremely important part played by light in agriculture makes 

 us regret that the actinometer should still l^e so little known. It 

 perfectly replaces the thermometer for agricultural purposes, but the 

 thermometer can not take its place. 



In his Annuaire for 1882 Marie-Davy gives the following study of 

 the development of cereals, wine, and other crops : 



Cereals. — The cereals offer a great number of varieties, and this 

 number increases annually, but often the differences that we see be- 

 tween them are due to certain influences of the soil and climate 

 which disappear by change of locality. However, there are some 

 varieties whose qualities have been fixed by long-continued cultiva- 

 tion in the ordinary way or by long-continued selection, and which 

 jjresent decided advantages for the specific climates. 



The varieties brought from the south are more sensitive to cold 

 than those from the north, and can not be propagated without special 

 precautions in higher latitudes or at greater altitudes than belong 

 to the localities where these varieties were gradually developed. The 

 varieties brought from the north are generally more precocious and 

 suffer more from dryness. The expressions " early " or " late " have 

 reference to their behavior in the new localit_v. The grain brought 

 from the south comes to maturity at a later date than that raised in 

 the north. 



Influence of heed and licjht on development of wheat. — We shall 

 divide the development of wheat into four phases, whose dividing 

 epochs are the processes of (1) sowing and germination, (2) heading 

 out, (3) flowering, and (4) ripening. According to Gasparin the ger- 

 mination of wheat begins when together with the necessary moisture 

 it also enjoys a temi)erature in excess of 5° C., and it sprouts when it 

 has received a sum total of effective mean daily temperatures (above 

 5° C.) equal to 84° C. Its sprouts shoot above the soil a few^ days 

 later. Some wheat sown by Marie-Davy April 23, 1880, was up on 

 the 4th of May, the sum of the mean temperatures being 9()°, so that 

 the germinating sprout had taken about two days to grow from the 

 seed to the surface. In thy following table columns 2, 3, 4, and 5 

 show the duration in days of the period required for the germination 

 of wheat supposed to be sown at Montsouris in the different years on 

 four different dates — «, h^ e, d — as stated at the heads of the columns. 

 These durations are calculated to the nearest whole days, on the 



