102 Linnean Society. [Dec. S, 



Dr. Adolph Schlagintweit, at the request of the President, gave a 

 summary of some of the principal results of the investigations of 

 himself and his brother into the Vegetation of the Alps in con- 

 nexion with height and temperature, as contained in their " Unter- 

 suchungen ueber die physilialische Geographie der Alpen." 



He stated that very remarkable differences are to be observed in 

 the limits of the altitude of vegetation in the district of the Alps. In 

 the mean results for large divisions, we may plainly recognize the 

 influence of geographical position, as well as that of the nature of 

 the soil, and of the massiveness of the mountain range. The limit in 

 fact becomes higher the more we approach the southern and western 

 groups, a phsenomenon which is connected with the general changes 

 of cUmate. The mean temperature varies in these latitudes from 

 0*5° to 0*7° of Celsius for one degree ; and at the same time the 

 isothermal lines show an evident inclination from west to east. Many 

 very essential diflFerences cannot, however, be explained by geogra- 

 phical position alone ; another important influence is dependent on 

 the form of the mountain-range, the limits of vegetation being 

 generally connected with the mean magnitude of the elevation, and 

 reaching higher in massive and lofty groups of Alps than in the 

 lower chains. The favourable influence which the massiveness of 

 the elevation exercises on the vegetation, is essentially the same as 

 that which is also evidenced with regard to the temperature of the 

 air and soil ; and corresponds to the diff'erence which is remarked 

 between the climate of a plateau, and that of a ridge or free peak in 

 the neighbourhood. In diff'erent valleys or on the spurs of a moun- 

 tain remarkable difi'erences in the altitude of the limit of vegetation 

 often manifest themselves according to the exposure, the direction 

 of the wind, or the proximity of separate and extensive masses of 

 glacier ; but these influences are for the most part merely local, and 

 the general variations of the limit of vegetation dependent on the 

 massiveness of diff'erent groups of Alps are but little aff*ected thereby. 

 A comparison of the annual isotherms with the limits of vegetation 

 proves that the diff^erent groups of vegetation do not always 

 terminate at the same annual isotherm. With the exception of 

 the Beech, he showed that up to the height of Coniferce, these 

 limits in the Northern Alps are reached at warmer isotherms than 

 in the Central Alps ; and a somewhat lower mean temperature 

 is obser\'ed on corresponding points of the group of Monte Rosa and 

 Mont Blanc. This is immediately dependent on the fact that the 

 growth of plants is not determined alone by the mean temperature 

 of the year, but also by that of the seasons and of the months. The 



