73 PERIODIC PHENOMENA OF VEGETABLE LIFE. 



depend on the will of man ; these are the hay-harvest and the 

 cultivation of summer Cereals. Yet in comparing a number of 

 observations, we find that the differences in the periods of these 

 voluntary acts are still caused by relations of climate. The 

 hay-harvest gives the most irregular results and differences, 

 varying the least according to elevation. It is only from 6000 

 to 7000 feet that it shows a very considerable delay, which is 

 owing to the manner in which the meadows are turned to use.* 

 Up to 6000 feet the meadows are generally mown twice : it is 

 only in some of the deepest valleys that by irrigation and careful 

 cultivation three hay-crops are sometimes obtained. In more 

 elevated situations they are obliged to commence mowing as soon 

 as the Grarninese are in seed, in order that the second mowing 

 may be completed before the often premature fall of the first 

 snows of winter. From 6000 to 7000 feet we often meet still 

 with real Alpine meadows, which, however, are only once mown ; 

 this takes place from the beginning to the end of August, and 

 even as late as September, whilst some high Alpine meadows, 

 above 7000 feet, are only mown every two years. 



In order to show, at one view, the delays occasioned in the 

 development of vegetation according to altitudes in a general 

 manner,! I have inserted in the following table comparative 

 differences in regard to special periods of vegetable life. 



We may observe, that in general the delay in the periods of 

 vegetation is less in the spring months than towards the end of 

 the flowering, and thence to the ripening. of the fruit. The mean 

 difference in question is of two days and a half, and this pheno- 

 menon is more especially observable in different parts of isolated 

 valleys. The cause must be sought for in the more rapid fall of 

 temperature which takes place in those situations in the summer 

 months, as the more elevated parts are thereby colder in propor- 

 tion, and the development of plants consequently slower than at 

 the commencement of vegetation. 



reached by these plants, I have inserted some data on the vegetation of 

 meadows or on early spring flowers, without intending to indicate any 

 analogy between these latter phenomena and the former. 



* This only applies to meadows cultivated in the vicinity of the most 

 elevated habitations. For in some places Alpine meadows are met with 

 much lower down which are only once mown. 



+ It is only by comparing the means of a great number of observations 

 that any precise estimate of the influence of altitude on the development 

 of plants can bo obtained ; for isolated stations and particular seasons show 

 very great differences, from which many apparently contradictory result?- 

 might be obtained. 



