104 Linnean Society. [Dec. 3, 



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

 lono- series of years, and do not agree in different 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, 

 o-ave for the former resrion, the subnival, 224 species, for the latter, 

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

 in Glarus in Switzerland 2 1 9 and 1 2 . Many families, as for example 

 Boragine(E, Euphorbiacece, Geraniacece, Labiatce, Liliacea, SteUatce, 

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

 diminish evidently and sometimes very strikingly in species in rela- 

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

 diflFerences are found in relation to height. A remarkable relative 

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

 Saxifrageas and Primvlacece ; and may also be remarked in Cam- 

 panulacece, Caryophyllete, Composita;, GentianecB, 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 glacialis and ^. Helvetica, Cerastium latifolium, Cherleria sedoides. 

 Chrysanthemum alpinmn, Gentiana Bavarica, Ranunculus glacialis, 

 Saxifraga bryoides, S. oppositi/olia, Siletie acaulis, &c. &c. The 

 extreme limit of Mosses is in general little above that of phaneroga- 

 mous plants. The last Lichens are to be found on the highest summits 

 of the Alps, attached to projecting rocks, without any limitation of 

 height. The number of species and varieties, up to this time between 

 40 and 45 species, which have been found in the Alps between 

 10,000 and 14,780 Paris feet, is not inconsiderable, but this vege- 

 tation is limited to very few spots, surrounded by extensive masses 



