M. Berghaus on the Epochs of Vegetation. 185 



PI ice — Absolute Height. Period of Sowing. Efflorescence. 



Harvest. 



Oats, Avena satira. 



Feet. I 



Valley of the Elbe, 350-400 April 1.-30. June l.-July 8. July 26.-Sept. 6. 



Freiberg, . 1000-1200 ! April 20.-May 20. ! July 15.-25 I Aug. 15.-Sept. 15. 



Annabel'} 100 °- 2000 ; A P ril 20.- May 25 J July £4.-Aug. 16. Sept. 6-28. 



Wiesenthal, . 2700-2800 May 16.-31. July 30.-Aug. 16. Sept. 6 28. 



Bakley, Eordeum testivum. 



Valley ofthe Elbe, 350-400 .' April 14.-May 10. 

 Freiberg, . 1000-1200 May 4.-16. 

 Marienberg,&c 1900-2800 May 5.-18. 



June 17.-July 19. 

 July 25.-Aug. 10. 

 July 30.-Aug. 15. 



July 18.-Aug. 19. 

 Aug. 25.-Sept. 16. 

 Aug. 25. -Sept. 20. 



The Potato, Solanam tuberosum (common, not early). 



Valley of the Elbe, 350-400 April lO.-Mav 20. June 9.-Aug. 1. Sept. 15.-0ct. 20. 

 Freiberg, . 1000-1200 April 6.-May 24. 



ESS?' } 1900-2000 April 19.-May 30. 

 AViesenthal, . 2700-2800 j May 12.-June 6. 



July l.-Aug. 26. I Sept. 20.-Oct. 28. 

 July 4.-Sept. 1. i Sept. 22.-Oct. 30. 

 Aug. 18.-Sept. 12. Sept. 28.-Oct. 30. 



In higher latitudes, in districts situated in the north of Ger- 

 many, the development of vegetation is less retai'ded than in 

 more southern positions ; the delay of the development of ef- 

 florescence between Hamburgh and Christiania amounts to 

 only 3.4 days for one degree's approach towards the north, 

 while that between Southern Germany and Smyrna in Asia 

 Minor, which is in the same parallel as the most southern por- 

 tions of Europe, amounts for the same space to 7.4 days. 



The cause of this difference arises from the different lengths 

 of the days, which in higher latitudes, during the Avarm period 

 of the year, increase in a much greater degree than they do 

 in southern parallels, by which the vegetation is hastened in- 

 to development more speedily ; and it is only in this way that 

 it is possible in higher latitudes for various summer plants to 

 reach their requisite maturity. 



Some plants exhibit in this respect remarkable differences ; 

 the activity of vegetation is not increased in equal proportions 

 in different plants by the same elevation of temperature. Plants 

 of northern climates are less retarded in their development at 

 the same low temperature than are plants of more southern 

 regions. If we compare Europe with America, wc find that 



