and the Means of ascertaining it. 



a more exact appreciation of the ordinary laws of the growth of 

 trees, and that this direct knowledge may throw light on many 

 parts of vegetable physiology and the art of forestry. I therefore 

 believe, that these inquiries may turn out to be useful ; but were 

 they merely curious, I would still think that they might not 

 be unworthy of being presented to the public, for curiosity 

 is one of the desires which the mind is more inclined to grati- 

 fy the more it is enlightened, and we have a thousand exam- 

 ples of unexpected advantages having arisen in consequence of 

 this noble feeling. 



Every one knows, that the vegetables designed for the forma- 

 tion of trees may be ranged under two great series. The first, 

 which is the more numerous, has a trunk composed of a 

 woody body and bark : it grows by the annual addition of a 

 new ligneous layer on the outside of the preceding layers under 

 the bark. In consequence of these new layers being the 

 youngest and the most outward, they have been called exogenous 

 in reference to their increase, and dicoii/ledonous when we al- 

 lude to their germination. The second series, on the contrary, 

 is composed of vegetables whose trunks, very cylindrical, and sel- 

 dom branching, merely present a woody body, properly speak- 

 ing without bark, whose outer fibres are older and harder, and 

 the inner younger and softer. They have been called endoge- 

 nous in consequence of this latter circumstance, which term is 

 employed when we allude to their growth, which is synonymous 

 with that of monocotyledonons, by which they are distinguished 

 when we speak of their germination. We shall succinctly ex- 

 amine the means of determinin<j the ase of individual trees of 

 both these classes, and conclude with a few words on vegetables 

 more humble in their appearance, but whose longevity presents 

 some singular ambiguities. 



1. Almost all the trees in temperate, and of course in the most 

 civilized, countries of the globe, belong to the exogenous class ; 

 and its history having therefore been more carefully studied, can 

 supply us with the most valuable information. It is known, 

 however, by means, of the truth of which there can be no doubt, 

 that exogenous trees grow each year by a new woody layer, 

 and that, in consequence, the number of concentric zones which 

 are seen on the transverse or horizontal cut of a trunk, may give 



