viii 



PREFACE. 



So little^ indeedj has the theory been countenanced 

 by botanists, that, to take Professor Balfour's excellent 

 Class-Booh of Botany (one of the fullest and most 

 recent of our systematic treatises), as a fair exponent 

 of the received doctrines in vegetable physiology, it 

 may be questioned whether the notice there taken of 

 the theory would lead any ordinary reader to do more 

 than bestow upon it a passing regard, or would suggest 

 to him the application here made of it (and obvious 

 in itself) to two practical questions respecting trees — 

 questions often put, and commonly felt to be ex- 

 ceedingly perplexing, viz., To what age do they 

 naturally live?" and, To what size do they natu- 

 rally attain?" Certain it is, that in considering 

 these questions. Professor Balfour himself makes no 

 allusion to the theory, and seeks for a solution of 

 them in a direction altogether different from that in 

 which it points. 



It is precisely because our prevailing notions, both 

 popular and scientific, differ so widely from what the 

 author believes to be the truth on this subject, that 

 he is induced to publish this volume. He is himself 



