PERIODIC PHENOMENA OF VEGETABLE LIFE. 67 



In some parts of the Alps the meltiug of the snow and reappear- 

 ance of vegetation may be influenced by the unequal repartition 

 of the fall of atmospheric meteors. In the southern portion of 

 the high ridges of the Alps in particular, the storms are generally 

 accompanied, in February, March, or April, by copious falls of 

 snow, and these large masses occasion delays in the melting of 

 the snow and the reappearance of vegetation, and the same 

 influence may be partially traced in the growth of the leaves and 

 the formation of flowers which immediately follow. 



The reappearance of vegetation often varies very much in dif- 

 ferent years. Thus in the spring of 1817, one of the latest, this 

 phenomenon took place several weeks later than the ordinary 

 mean, whilst on the contrary, in 1834, it was considerably in 

 advance of the same mean.* There are even greater irregu- 

 larities in the time of the last falls of snow in spring and the first 

 falls in autumn, as well as in the extremes of nocturnal cold in 

 certain years. At the foot of the Alps, from 1500 to 2000 feet, 

 passing falls of snow become very rare in the middle of May, or 

 at any rate at the end of that month ; so also is it with nocturnal 

 frosts. In autumn, the latter may come on suddenly very early, 

 whereby the cultivation of fruit-trees in many valleys, especially 

 on the northern side of the chain, becomes uncertain ; the fall of 

 leaves is also much hastened in consequence. 



Between 2000 and 3000 feet, the 15th of June gives an average 

 of extreme falls of snow, f The night-frosts of spring and autumn 

 are considerable in these regions, especially in deep valleys which 

 reach down to the regions of cultivation of Maize | and Buckwheat. 

 Where these frosts are frequent the cultivation of these plants is 

 much restricted, and much sooner ceases entirely. In the centre 

 of this region, 2500 to 2700 feet, the sharp night-frosts generally 



* As examples of these yeai-s, I may state that at Leugenfeld (3617 feet) 

 in 1817, sledges were still used in the beginning of May; at Fertheiseu the 

 meadows were not yet green towards the middle of May ; a similar delay 

 was observable at greater altitudes, so that every where journeys in the 

 Alps could only take place that year several weeks later than usual. 

 According to Heer there was still in the beginning of May, at Matt (2560 

 feet), deep snow which only melted towards the middle of the month. In 

 1834, on the contrary, the winter was mild. On the 31st of January there 

 was scarcely any snow remaining at Matt, and in places exposed to the 

 sun, the first flowers appeared of Anemone hepatica, Daphne Mezereum, 

 Tussilago alba, and Mercurialis perennis. 



+ For Kitzebiihl, Unger mentions an extreme fall of snow on the night 

 of the 16-17th June, 1830, which extended down to 2350 feet, and lay in 

 the morning an inch and a half thick. 



X Maize is in all climates very susceptible of spring and autumn frosts. 



f 2 



