68 DICOTYLEDONE^:. 



which swelled it into form. Thus we find that the 

 first formations of trees, viz. the pith and its sur- 

 rounding- layer of wood, is the first to become decom- 

 posed. Now, could the time which elapses between 

 the first year of the seedling, and the commencement 

 of internal decay be ascertained, it would be an ex- 

 cellent guide for the operations of the woodman, 

 merely for this reason, that he need never fell a tree, 

 until it was in its prime, nor delay this business till it 

 was too late. A timber tree is at its prime in the 

 year before it begins to decay ; if felled in or before 

 that time, it falls sound ; if after, it falls defective. 

 This part of the history of trees will be resumed in 

 another section ; but it may just be added here, 

 that the longevity is usually attributed to the suita- 

 bleness of the soil and situation in which they chance 

 to be placed ; but of this plausible opinion we have 

 no certain knowledge : for though rapidity of growth 

 and measurable bulk are certainly entirely owing to 

 these favourable circumstances ; still there is doubt 

 whether even the oak does not begin to decay at the 

 heart, as soon in a rich, as in a poor soil. In a rich 

 soil an oak may attain a great bulk in a compara- 

 tively short time, and be fit for the axe long before 

 one planted at the same time on a hill of inferior 

 soil ; yet, of the two trees, that raised on the most 

 suitable soil would be the most durable. 



Nearly allied to the Amentacece are the Juglandece, 

 of which the common walnut is the representative. 

 The North American hiccories, Garya, are elegant 



