PERIODIC PHENOMENA OF VEGETABLE LIFE. 



71 



few observations have indicated to us clearly similar relations for 

 other fruit-trees. For Cereals, account may also be taken of the 

 time which elapses between sowing and reaping. Striking dif- 

 ferences are observable in this respect according to geographical 

 latitude, as well as according to elevation. I have here placed in 

 juxtaposition with these phenomena, as recorded in the Alps, some 

 observations which Grisebach* has published after Daum and 

 Parlatore. 



The progression from southern Italy to the north of Germany 

 here produces the same effect as a considerable increase in 

 elevation. In both cases there is a great prolongation of the 

 period of vegetation in Cereals. At 5000 to 5200 feet, the 

 extreme limit of Rye, it often remains a whole year in the 

 ground. 



These comparisons can only be established in respect of 

 countries whose climates are analogous in the repartition of heat 

 according to seasons. The growth of Cereals near their limits 

 towards the north can no longer be compared with the same 

 phenomena in the Alps, for in the usually excessive climate of the 

 north of Siberia, the period of vegetation of Cereals is on the 

 contrary shortened. 



Besides the phenomena of which the periods are solely occa- 

 sioned by relations of climate, I have, in the table of their mean 

 commencements (above, p. 65,)} inserted some others which 



* Report on the progress of Vegetable Geography for the year 1845. 

 Berlin, 1847. 



+ I have here taken the period of the harvest in preference to that of 

 maturity, for the purpose of comparison with southern stations, the former 

 being there rather later than the period of maturity strictly speaking. In 

 the variations in the time of sowing, the data given, especially for autumn, 

 can only give the most usual changes in these relations. 



% In some parts of that table, as, for instance, opposite the foliations of 

 Fraxinus excelsior and the flowering of Viola odorata, at the heights not 



