XVlll 



CONTENTS* 



PAGE 



age and size. References to very old and large 'trees — 

 yewS;, courbarils, American cedar, boabab, gum-dragon 

 tree, deciduous cypress, the banyan, enormous plank of 

 timber, Wellingtonia gigantia. 



Question— "Why, if this theory be sound, very old and 

 very large trees are not more numerous than they really 

 are] Explanation— All trees subject to accidental" 

 death from extraneous causes, and are sooner or later, and 

 some kinds of trees more speedily than other kinds, thereby 

 destroyed. Enumeration of these causes. 



LETTER VIII 68 



Evidence adduced in support of the theory. Two-fold — Is^, 

 that the growths emanating from the buds constitute seve- 

 rally perfect and independent plants, and that a succession 

 of such plants may be kept up from year to year for ever 

 from buds alone ; and, 2ndlyy that at the end of the year, 

 the plants thus evolved (save the buds only) die and never 

 live again. 



First branch of the evidence taken up and pursued. The 

 produce of the buds includes all the parts entering into the 

 constitution of the most perfect seedling plants, viz. : stems 

 and roots, leaves, flowers, seeds and buds. The bud can 

 evolve the seed. Illustrations furnished by the potato, 

 the strawberry, and the processes of grafting, slipping, and 

 layering. Mr Knight's view as to the dying out " of fruit- 

 trees opposed to the theory : his view erroneous. 



LETTER IX 79 



Second branch of the evidence taken up- and pursued, viz. : 

 that at the end of the year the plants emanating from the 

 buds die. The only parts of the plants that then remain 

 are the stems and roots, the other parts having dropped 

 off. Proofs that these stems and roots die at the 

 end of the year. Gfeneral considerations as to the very 

 transient duration of vitality in all organised structures : 

 the continued vitality of any structure only possible by a 

 continual change of substance, called by physiologists in- 

 terstitial or molecidar nutrition. This process obtains in 



