198 



De Candolles Essay 



[April, 



centre to the circumference ; on this slip I marked with a pen or pencil the 

 meeting of each zone, the size of the pith, and that of the bark ; writing on it 

 the name of the tree, the country to which it belonged, and any particulars which 

 deserved notice. My collection of these slips, (which have no small resemblance to 

 the measures preserved in a tailor's shop) gives me an exact estimation of the 

 different growth of different trees, and the means of comparing one with another. 

 I take the precaution of marking in a more decided manner every tenth ray, which 

 gives mc the average rate of increase for every ten years growth. 



My measure, being taken from the centre to the circumference, expresses the 

 radius. I double it, if I require the diameter ; I take six times if I wish to have 

 the circumference of the woody substance. It is not so useful, except in some 

 particular instances, to make these observations on young trees ; for in working 

 on the older ones, of which every species may be procured, there is the 

 advantage of being able to judge of the trees in every stage of their growth. As 

 it would be inconvenient to publish an exact copy of these slips of paper, which 

 are sometimes several feet long, I shall give an idea of their results, by the following 

 table : [We have converted the French lines into English measures. — Ed.] 

 Table of the growth of some exogenous trees, as measured by their increase of dia- 

 meter in periods of ten years, expressed in inches and tenths, English. 



Years of age. 



Oak 



(peduncu- 



lata,) 

 aged 130 

 years. 



Oak 



(Sessili- 



flora) 



aged 210 



years. 



Oak 



(ditto,) 



aged 333 



years. 



Larch, 



a>ed 255 



years. 



Elm, 



aged 335 



years. 



Fir, 



aged 120 



years. 



Yew, 



aged 71 



years. 



I 



1 to 10 



4.8 



0.9 



1.6 



4.2 



1.4 



3.6 



0.7 



10 to 20 



5.5 



1.4 



2.9 



5.4 



3.8 



4.7 



1.0 



20 to 30 



4.8 



2.0 



3.4 



5.1 



5.1 



4.6 



1.1 



30 to 40 



5.3 



1.1 



3.3 



6.4 



6.4 



3.9 



0.9 



40 to 50 



4.2 



1.2 



2.1 



4.0 



7.7 



3.0 



0.6 



50 to 60 



3.9 



1.3 



1.1 



5.0 



6.8 



3.1 



1.1 



60 to 70 



4.9 



1.0 



0.8 



4.0 



6.9 



1.6 



0.7 



70 to 80 



3.9 



1.0 



0.8 



2.6 



5.8 



1.5 





80 to 90 



2.8 



0.8 



0.7 



2.6 



5.2 



1.2 





90 to 100 



2.8 



0.8 



0.7 



2.2 



3.9 



1.2 





150 to 160 





0.7 



0.7 



1.9 



1.7 







200 to 210 





0.8 



0.7 



2.0 



3.0 







250 to 260 







0.7 



1.8 



2.1 







300 to 310 







0.8 





1.4 







320 to 330 







0.7 





1.9 







It results from these observations, that in the advanced periods of their life, 

 trees continue to form layers which do not yield in thickness to those of a middling 

 age ; that every species, after having grown rapidly in its youth, appears at a 

 certain age to attain a stated and regular growth. In fact, a tolerably good 

 reason may be assigned for these differences, by assuming, that during the 

 first period, that is to say, before 60 or 80 years, the roots and the branches of 

 forest trees, not being confined by their neighbours, grow freely ; but" that, after 

 that age, they grow less rapidly, on account of their encountering the roots and 

 branches of neighbouring trees ; finally, that inequalities of growth are owing 

 either to the quality of the zone or stratum of earth from which the main portion 

 of the roots are drawing their nourishment, or to the circumstance of the neigh- 

 bourhood of the tree being more open and clear at some periods. Such calcula- 

 tions made on a great variety of species, and on individual trees of every species, 

 would give the most interesting results regarding the progress of vegetation : 



