II. 



VITALITY OF SEEDS. 

 "VTOTHING in connection with forests has at- 

 _[)| tracted more attention than the springing up 

 of a different kind of timber when one forest growth 

 is removed by the ax or fire. This has been attrib- 

 uted to the exhaustion of certain elements in the 

 soil, rendering necessary a natural rotation of 

 species, in order to maintain the continued growth 

 of vegetation, thus furnishing a grand lesson from 

 nature on tJie importance of a rotation of crops. 

 Without discussing at present the truth of this 

 explanation, or the frequency with which such a 

 natural rotation of forests actually occurs, the case 

 is presented as a familiar illustration of the appear- 

 ance of plants where none of the same kind were 

 known to exist before. The apparently spontane- 

 ous growth of immense quantities of Fireweed, and 

 other species rarely found in either cultivated land 

 or natural forests, on ground which has been newly 

 cleared, is a similar instance of the growth of vege- 

 tation where there is no visible supply of seed. 

 Such cases were formerly regarded as conclusive 

 evidence of spontaneous generation, a belief held 



(14) 



