390 CONIFERJE. 



also is another important substance, obtained by charring 

 the wood, during which process the tar flows from it in 

 the form of a thick black fluid, which is collected in 

 reservoirs or casks made to receive it. 



The geographical distribution of this section of the 

 Coniferee. is very extensive, but the great majority of the 

 species are found in the temperate parts of the northern 

 hemisphere ; some species extend to high latitudes, reaching 

 nearly to the icy regions of the arctic circle, or if grow- 

 ing in temperate and warmer districts, inhabiting the 

 mountains, where they occupy a zone so elevated as to 

 reduce the climate to the degree of temperature equiva- 

 lent to that of a higher latitude. Even the few species 

 which grow within the tropics are always found in lo- 

 calities rendered comparatively cool, either by their ele- 

 vation, or their proximity to the sea. The social nature 

 of the Abietina is shown by the vast forests which cover 

 extensive tracts of country, to the exclusion of almost 

 every other tree. These prevail throughout all the north- 

 ern parts of Europe, consisting sometimes of the common 

 Pine, Pinus sylvestris, which is also the indigenous fir of 

 Scotland, where it still occupies extensive districts ; at 

 others, of the spruce, Abies excelsa. In parts of Germany 

 the Pinus Austriaca is the prevalent species ; in others, 

 Pinus pcdlasiana. In the Swiss and the Tyrol Alps 

 the larch abounds, as well as the Picea joectinata, perhaps 

 the finest of the European firs. In North America, also, 

 enormous tracts of country are wholly occupied by forests 

 of Abietinte, among which those of the Pinus strobus, 

 Weymouth Pine, which furnishes the white deal of com- 

 merce, and is largely imported into Britain from our Cana- 

 dian provinces, are, perhaps, the most extensive. In Asia, 

 the great chain of the lofty Himalayas, and the moun- 



