121 



down the principle that with approximately equal latitude and elevation, the 

 temperatures above 0° in shade are higher for the same developmental 

 phase (time of blossoming, defoliation, etc.) in the western parts of Europe 

 than in the eastern ones. Observations show that in Europe the length of 

 the growth period decreases toward the northeast and increases towards the 

 southwest. Because of the many mountain chains and plateau-like inter- 

 ruptions the phenomenon is less clearly evident in western Europe than on 

 the great level plains of Russia. Kowalewski's^ very remarkable work re- 

 ports on this phase. This is based on the statements of 2200 agriculturalists 

 scattered throughout all parts of European Russia, who had reported the 

 time of sowing and harvesting of the grain. Since cultivation must be 

 adapted to climatic conditions, the usual times for sowing and harvesting 

 show the existing vegetative conditions. 



The sowing of winter rye takes place in the southern part of the Gov- 

 ernment of Kherson on the 15th of September-, at Archangel, on the first of 

 August. The localities of simultaneous plantings of winter rye do not run 

 parallel to the degrees of latitude, but are inclined from N. W. to S. E. ; 

 therefore, they run almost in the same direction as do the isocheims. The 

 difference in the time of harvesting winter rye in the far north (Archangel) 

 and in the south (Kherson) extends, like the time of sowing, over a month 

 and a half. The seeding period for summer grain in the far north is one- 

 third to one-fourth as long as at the southern limit. At the western it is two 

 to two and a half times longer than at the eastern. The time of harvesting in 

 the north is hkewise one-third as long as in the south ; in the west once and 

 a half to twice as long as in the east. The localities of simultaneous ripen- 

 ing of summer grain run from S. W. to N. E., corresponding therefore in 

 their direction with the isotheres. 



The growth period in southern and southwestern Russia is only 85 to 

 no days for rye, buckwheat, flax and barley, — but no to 125 days for sum- 

 mer wheat, millet, oats and peas. Sugar beets, maize and potatoes have the 

 longest growth period, — 150 to 165 days. Thus, in the south, the longest 

 growth period is almost twice as long as is the shortest. On the other hand, 

 in the north, the periods concerned are not only shorter everywhere but are 

 also more simultaneous. In the far north and northeast the difference be- 

 tween the longest and the shortest growth periods does not exceed 10 to 20 

 days. 



For the same cultivated plant, in European Russia, the rate of develop- 

 ment increases on the average with the latitude. Thus, for example, oats in 

 the Government of Kherson (south) have a growth period of 123 days, 

 wheat and barley one of no days. In the north, however, (Archangel) the 

 growth period of oats decreases to 98 days, that of wheat to 88 days, of bar- 



1 Kowalewski, W., Ueber die Dauer der Vegetationsperiode der Kulturpflanzen 

 in ihrer Abhangiglveit von der geograpliischen Breite und Lange. Arb. d. St. Peters- 

 burger Naturforscherges., XV, 1884 (russisch), cit. Bot. Centralbl., 1884, No. .^1, 

 p. 367. 



2 All dates are given old style as still used in Russia. 



