CAMPHOR-TREES. 137 



trees are all included, and laurels with respect to Switzerland. 

 The most important are the camphor- and cinnamon-trees, as 

 the homologous Miocene species are common everywhere, and 

 furnish us with the best standard for ascertaining the climate. 

 Both species are inhabitants of Southern Japan ; the camphor- 

 tree also lives in China. In the gardens of Madeira the cam- 

 phor-tree grows to a considerable size ; it also thrives in Sicily 

 (at Palermo) and at Pisa and Florence, where, however, it never 

 ripens its fruit. At Padua it requires to be protected in winter 

 by a glass roof. In the Botanic Garden at Montpellier it was 

 frozen down to the ground in the winter of 1853-54, but threw 

 up fresh shoots from the bottom. On the Isola Bella of the 

 Lago Maggiore, which is celebrated for its mild climate, a fine 

 camphor- tree stands in the open air ; but it is protected from 

 the north wind by a high wall, and can be partly covered in 

 winter. In the winter of 1856 the branches were killed by a 

 frost of 14 Fahr. ; so that they had to be pruned back to the 

 main stem, which, however, pushed forth again ; and in the 

 autumn of 1864 Prof. Heer saw the tree in full foliage. It is of 

 the size of a large plum-tree. In the same neighbourhood, at 

 Pallanza, there is also a camphor-tree in a sheltered situation in 

 a garden ; but it has to be wrapped up in straw in the winter ; 

 and even with this precaution the young shoots are frozen, and 

 require to be cut back nearly every year. Like the tree of the 

 Isola Bella, it flowers annually, but without ripening any fruit. 

 The camphor-tree therefore requires for its development a 

 warmer climate than that of Provence and North Italy. To 

 thrive it needs a mean annual temperature of 18-19 Cent. 

 (or 64 G> 4-66'2 Fahr.) ; and its northern limit cannot pass be- 

 yond the isotherm of 15 Cent, (or 59 Fahr.). This applies 

 also to the Canarian laurel and the vinhatico ; and even the 

 European laurel will not stand the winter of Switzerland. 



A careful comparison of the characters of the vegetation of the 

 different stages of the Miocene shows that during that period 

 some diminution of temperature took place. We have already 

 seen (vol. i. pp. 316, 317) that the evergreen trees form about 

 three fourths of the whole in the Aquitanian stage, and only 

 about half in the (Eningian stage, and that in the latter the 



