148 Linncean Society. 



the air, of the soil, and in the climate generally (which concur to 

 disturb the Coniferce at greater heights) produce a diminution 

 of their yearly growth ; but the different nature of the soil has also 

 great influence on their growth. The mass of well-decomposed 

 earth, the presence of boulders or firm rock, the exposure of the 

 locality, the humidity of the soil, and in some degree also its inclina- 

 tion, have so great an influence on the growth of the tree, and are 

 moreover especially in the lower regions so irregularly distributed, 

 that the influence of elevation, which should be most closely con- 

 nected with the changes of climate, may be and is partially oblite- 

 rated. Very frequently indeed in investigations of the geography 

 of plants, a similar concurrence and a mutual correlation of the 

 various causes by which the changes of vegetation are produced, are 

 to be recognized. The observation of the progress from year to 

 year shows that very frequently considerable variations occur in the 

 amount of growth in separate stems. These are not, however, con- 

 nected with definite years of the development, but irregularly dis- 

 tributed during the life of a tree. As they commonly extend over a 

 long series of years, and do not agree in diff'erent trees for definite 

 numbers of years, they cannot be produced by the climatic circum- 

 stances of unfavourable years. The larger oscillations of growth are 

 dependent, on the contrary, on the nature of the soil, inasmuch as 

 the roots during their extension meeting with more or less favourable 

 and rocky spots, the productiveness of a tree may be essentially 

 changed during many years. 



An enumeration of all the phanerogamous plants found in the 

 Upper Moll district (in the Tauern, in Upper Carinthia) at between 

 7000 to 8000 Paris feet high, and between 8500 to 10,000 feet, 

 gave for the former region, the subnival, 224 species, for the latter, 

 the nival, 32 ; while Prof. 0. Heer obtained from the same regions 

 in Glarus in Switzerland 219 and 12. Many families, as for example 

 Boraginea, Euphorbiacea, Geraniacea, Labiatce, Liliaceee, Stellatce, 

 Umbellifera, &c., compared with the lower regions and with Germany, 

 diminish evidently and sometimes very strikingly in species in rela- 

 tion to the sum of Phanerogamce. In some others no such regular 

 differences are found in relation to height. A remarkable relative 

 increase of species in connexion with increased elevation, is found in 

 SaxifragecB and Primulacea; and may also be remarked in Cam- 

 panulacece, Caryophylleee, Compositce, Gentianecs, and others. This 

 depends, not on an absolute increase of species of these families, but 

 on a diminution of the species of the other families. Monocotyledones 

 generally diminish with height in relation to Dicotyledones ; except 

 that in the nival region and in the highest localities this proportion 

 appears to be somewhat undefined. The covering of snow also is 

 not completely universal in the high regions. In spots free from 

 snow and furnished with earth, phanerogamous plants, as well as 

 Mosses and Lichens, are found far above the snow-line. Among 

 the species which are found at the extremest limits in the Central 

 and Southern Alps, at 10,000 to 11,000 Paris feet high, are Andro- 

 sace glaciaUs and ^. Helvetica, Cerastium lati/olium, Cherleria sedoides. 



