THE FIR TRIBE. 



319 



social among themselves, they are strictly ex- 

 clusive as it regards other trees ; they are generally 

 found covering extensive tracts of coimtry, and 

 being evergreen, they shut out the light from 

 every other tree that attempts to germinate 

 beneath their unfriendly shade. For the most 

 part, they stand as close together as is consistent 

 with their healthy growth ; hence they not only 

 borrow from each other a firmer hold of the 

 ground by interlacing their roots, but prevent a 

 free circulation of air round their stems, and 

 consequently the small lateral branches which are 

 formed, soon grow sickly and perish. This 

 effect is perhaps increased by the rarified state of 

 the air at great elevations. The decay of the 

 lateral branches does not, however, in any case, 

 extend to the bole, for the dead wood of the 

 Firs does not rot, as is the case in other trees, but 

 as soon as vegetation ceases, the consistence of the 

 wood changes ; the sap disappears, and the wood, 

 already impregnated with resinous juice, becomes 

 surcharged to such a degree as to double its 

 weight in a year."^ Meanwhile the trunk in- 

 increases in dimensions, and encloses the hard 

 stump in its substance ; and hence originate the 

 dark circular knots, so common in most kinds of 

 Fir-wood. In the main stem the woody fibres 

 are less close than in most other trees ; the effect 

 of which is, that the wood is more elastic, 

 bending before the blast, but not breaking ; and 

 the resinous nature of the juices in every part of 

 the tree defies the infiuence of the severest 

 frost. 



On examining the leaves, we find an equally 

 * Michaux. 



