190 VEQETABLE ORGANOGRAPHY. 



fibres of the interior ; then the first-formed zone hardens, 

 and cannot increase more in diameter the following 

 year ; and, by the same causes, the second zone hardens, 

 and forms a ring above the first : this takes place in all 

 the following years, so that the stem is strictly cylin- 

 drical, its external part being composed of perfect wood, 

 and its interior of fibres not as yet hardened. 



A rude image of this evolution of the Palms can be 

 made by comparing them to the parts of a telescope, 

 which can be disjointed from one another; also by 

 likening it to the bark of an Exogen, which grows inde- 

 pendently of the v/oody body ;* but in these comparisons, 

 and also in my description, I have been obliged, m order 

 to make myself understood, to speak of layers ; and these 

 layers, although they might appear really to exist, are not 

 always distinct enough to be perceived. We see, then, 

 from this description, that if we were able to count the 

 layers or the fibres of the transverse section of a Palm, 

 the solidified layers would be, throughout the whole 

 length of the tree, in proportion to the age, and the rings 

 wovdd present the number of years the tree had lived ; 

 but it is impossible to distinguish them. "We may know 

 the age of Palms in a very simple manner — viz. by 

 counting the rings, which are often marked externally 

 on the trunk, and which are the cicatrices of the leaves ; 

 but these may imperceptibly disappear, so as not to be 

 able to be counted in old trees. As the annual elongation 



* M. Lestiboudois has followed this metaphor, and considered it as a 

 reality ; but he has not borne in mind that the trunk of Palms can by no 

 means be compared to the bark of Exogens, since the ascending sap con- 

 stantly rises by the trunk, whilst it never does so by the bark. This well- 

 known fact is sufficient to prove that this trunk is more analogous to the 

 woody than to the cortical body of our trees. The difference between these 

 two classes of bodies is confirmed by anatomy ; for the trunk of Palms 

 presents tracheas, and striped and dotted vessels, like the woody bodies of 

 Exogens. 



