CHAP. II. 



EXOGENOUS STEMS. 



75 



either side must necessarily lead to the falsest inferences. For 

 example, I have now before me four specimens of wood, taken 

 almost at hazard from among a fine collection, for which I am 

 indebted to the munificence of the East India Company. 

 The measurements of either side, and their age, as indicated 

 by the number of zones they comprehend, are as follows : — 



Benthamia fragifera 

 Pyrus foliolosa - - 

 Magnolia insignis - 

 Alnus napaleiisis 



Diameter of 

 Side A. I Side B. 



9 line's. 



8 lines. 

 1 1 lines. 

 II lines. 



36 lines. 



22 lines. 

 20 lines. 



23 lines. 



Total, 



45 lines. 



30 lines. 



31 lines. 

 34 lines. 



Real 



Aire, or 

 No. of Zones. 



40 



sr, 



17 

 8 



Now, in the first of these cases, suppose that a portion of the 

 side A. were examined, the observer w^ould find that each 

 zone is 0"225 of a line deep ; and, as the whole diameter of 

 the stem is 45 lines, he would estimate the side he examined 

 to' be 22'5 lines deep ; consequently, he would arrive, by cal- 

 culation, at the conclusion, that, as his plant was one year 

 growing 0*225 of a line, it would be a hundred years in 

 growing 22*5 lines, while, in fact, it has been only forty years. 

 And so of the rest. 



When we hear of the Baobab trees of Senegal being 5150 

 years old, as computed by Adanson, and the Taxodium dis- 

 tichum still more aged, according to the ingenious calculations 

 of Alphonse De Candolle, it is impossible to avoid suspecting 

 that some such error as that just explained has vitiated their 

 conclusions. 



To the characters above assigned to the stem of Exogenous 

 plants there are several remarkable exceptions, some of which 

 have been described by botanists ; others are mentioned now 

 for the first time. 



Mirbel has noticed the unusual structure of Calycanthus 

 {Annates des Sciences, vol. xiv.), in the bark of which, at equal 

 distances, are found four minute extremely eccentrical woody 

 axes, the principal diameter of which is inwards ; that is to say, 

 next the wood. The existence of this structure, noticed by 

 the discoverer only in C. floridus, I have since ascertained in 

 all the other species, and also in Chimonanthus. Gaudichaud 



