118 ORIGIN OF THE WOOD. 



It consists of a central portion similar to common endo- 

 gens, but this column is surrounded by bundles of vascular 

 fibres, the bundles having no connexion with each other, 

 corresponding, in the opinion of the Profeiisor, to the aerial 

 roots of the Pandanus. We know of no other theory, which 

 explains the putting forth of roots from buds when plant- 

 ed, as in the case of the Multicaulis. TJiese will put forth 

 roots immediately from the bud, and in all essential points 

 agree exactly with the germination of the seed. A complete 

 bud of a Multicaulis will germinate, when all the substance 

 of wood and bark is removed, which does not enter into the 

 composition of the bud. The vitality of most buds seems 

 to be much less, and in some cases cannot be made to ger- 

 minate at all when removed from the parent stock. Whence, 

 we would ask, come the roots from a bud if they are not 

 the direct production of the bud? We can conceive of no 

 other solution to the phenomenon, and when the bud is re- 

 moved from the parent, the fibres it would otherwise have 

 sent through the trunk become proper roots at once. From 

 the above theory we are cautioned against excessive pruning, 

 where we wish to obtain substantial stocks ; for all other 

 things being equal, the growtli of the body of a tree will be 

 in direct proportion to the leaves, which of course, will be 

 in proportion to the branches. If these are removed to a 

 great extent, the growth of the tree is retarded, if not other- 

 wise injured. 



148. The duration of vegetable-s is exceedingly various. 

 Some come forth during the darkness of a single night, and 

 wither and die on the approach of day ; others go through 

 their different stages of growth to perfection in a few days, and 

 disappear. Some require the length of several months for 

 the same operation, and others of two years, while others 

 still come to perfection only after several years, and then 

 are continued isi existence for indefinite periods. The latter 

 is the case with forest trees. We see nothing, theoretically 

 considered, opposed to the unlimited duration of Exogen- 

 ous trees. Each year's growth may be considered a distinct 

 individual huvinjr in itself all the elements for the production 

 of a similar individual, which, when produced, has no ne- 

 cesssary dependence upon its progenitor ; since each layer 

 of any tree has been endowed during its time with all the 

 productive functions of the individual. lUit to this unlimit- 

 ed duration of vegetables, nature off*ers impassible barriers. 

 The action of the elements, the attacks of insects and 

 larger animals, the exhaustion of the soil by other vegets^- 



