52 THE MODERN PERIOD. 



have attained their full height, these, and other trees capable of 

 attaining a greater magnitude, overtop them, and finally cause their 

 death. The forest has then attained its last stage, that of perfect 

 renovation. The cause of the last part of the process evidently is, 

 that in an old forest, trees of the largest size and longest life have 

 a tendency to prevail, to the exclusion of others. For reasons which 

 will be afterwards stated, this last stage is rarely attained by the 

 burned forests in countries beginning to be occupied by civilized 

 man, and it is evident that many circumstances may occur which will 

 prevent this restoration of the primeval forest. 



In accounting for the presence of the seeds necessaiy for the 

 production of the second growth, we may refer to the same causes 

 which supply the seeds of the smaller plants appearing immediately 

 after the fire. The seeds of many forest trees, especially the poplar, 

 the birch, and the firs and spruces, are furnished with ample means 

 for their conveyance through the air. The cottony pappus of the 

 poplar seems especially to adapt it for this purpose. The seeds of 

 the wild cherry, another species of frequent occurrence in woods 

 of the second growth, are dispersed by birds, which are fond of the 

 fruit ; the same remark applies to some other fruit-bearing species of 

 less frequent occurrence. When the seeds that are dispersed in these 

 ways fall in the growing woods, they cannot vegetate ; but when they 

 are deposited on the comparatively bare surface of a barren, they 

 readily grow ; and if the soil is suited to them, the young plants 

 increase in size with great rapidity. 



It is possible, however, that the seeds of the trees of the second 

 growth may be already in the soil. It has been already stated, that 

 deeply-buried tubers sometimes escape the effects of fire ; and, in 

 the same manner, seeds embedded in the vegetable mould, or buried 

 in cradle hills, may retain their vitality, and, being supplied by the 

 ashes which cover the ground with alkaline solutions well-fitted 

 to promote their vegetation, may spring up before a supply of seed 

 could be furnished from any extraneous source. It is even probable 

 that many of the old forests may already have passed through a 

 rotation similar to that above detailed, and that the seeds deposited 

 by former preparatory growths may retain their vitality, and be called 

 into life by the favourable conditions existing after a fire. 



If, as already suggested, forest fires, in the uncultivated state of 

 the country, be a provision for removing old and decaying forests, 

 then such changes as those above detailed must have an important 

 use in the economy of nature, since by their means different portions 

 of the country would succeed each other in assuming the state of 



