PEKIODIC PHENOMENA OP VEGETABLE LIFE. 87 



to eightfold.* At an elevation of 3000 feet it is reduced to five 

 or sixfold ; at 4000 feet, and a little above, the produce diminishes 

 very much, particularly in respect of Wheat, which meets here with 

 its limits, whilst at the upper limits of all grain cultivation the 

 produce of Winter Rye and Barley, even in a mean of favourable 

 years, sinks down to two or three and a half-fold. It there 

 happens in the worst years that the corn either does not ripen at 

 all, or barely produces the quantity sown. The produce of Maize 

 shows very great variations. At 2000 feet it amounts to about 

 eighty-five times the seed ; at its mean limits of 2500 to 2700, it 

 still produces from fifty to sixty-fold ; whilst at the highest isolated 

 points where it is cultivated (3500 feet), it not unfrequently 

 happens, that from a deficiency of autumn heat, or the early 

 occurrence of night frosts, it does not ripen at all.f 



Besides the climateric changes, especially the diminution of 

 temperature, the mode of cultivation, at great elevations, affects 

 considerably the produce of Cereals. In the lower parts of the 

 Alps a rotation of crops can he carried out with advantage, and in 

 the broad flat valleys and their neighbourhood may be found a 

 regular and tolerably extensive course of agriculture. But in the 

 more elevated spots the inclination and inequalities of the soil 

 give room only for very small fields, which are worked with the 

 hoe. By a rich supply of dung, J however, it is endeavoured to 

 form a very favourable soil. 



In the more elevated cultivated spots, the results are still far 

 more unfavourable, when we calculate them by a comparison of 

 the produce of a given surface, as in these situations, in conse- 

 quence of the inclination of the soil and the abundance of weeds, 

 the crops are vexy much thinner on the ground. 



The inclination of the soil is very considerable, and in many 



* The produce, however, under the most favourable external circum- 

 stances may, for the ordinary kinds of grain, rise to twenty-five times the 

 seed, as, for instance, in the case of wheat in Mexico. See Humboldt, 

 Essal surla Nouvelle Espagne, vol. ii. p. 429. 



+■ Such attempts at cultivation may be seen, for instance, at Sagritz, at 

 an elevation of 3500 feet; mean temperature, 6,2° centigrade, in summer 

 14,4° centigrade, in autumn 6,2° centigrade. In the tropics where maize 

 is grown at an elevation of 2800 feet in South America (mean annual 

 temperature 27,5° to 14° centigrade), it produces, according to Codazzo, 

 238-fold ; in Abatia sometimes 190-fold. Boussingault, Economie rurale, 

 vol. ii. 



Z For the highest fields an abundant supply of dung can generally be 

 obtained from the adjoining chalets ; in the deep valleys, on the contrary, 

 where the greater portion of the cattle is usually sent during the summer 

 to the Alpine pastures, there is often a considerable scarcity of dung. 



