208 



HEIGHT AND THICKNESS. 



[BOOK 



between Nos. 2 and 4) to at least a third, or (as between 

 Nos. 1 and 4) to one-half. 



"It would be a highly interesting contribution to science, if 

 numerous comparative calculations and measurements were 

 made in different countries, and under every variety of exter- 

 nal conditions, for the accurate determination of the limits of 

 this disparity in the growth of trees of the same species. The 

 height of these trees has probably been exaggerated, when 

 that of Araucaria imbricata has been stated to reach 260 

 feet, although 220 feet have also been given as that of Arau- 

 caria excelsa. In all the rest, the average height scarcely 

 exceeds that of our Spruce and Silver Firs, which under very 

 favourable circumstances will attain from 160 to 180 feet. 

 The Scotch Fir (P. sylvestris) and Larch, with many others, 

 though not of such lofty growth, nevertheless exceed 100 feet, 

 and there are very few which do not reach 50 feet. The 

 relative proportion of diameter to height varies extremely, as 

 may be seen from these examples : 



This table shows that the proportion between height and 

 thickness varies from 1 : 3' 5 to 1 : 120, and the difference 

 with respect to dimensions which has been heretofore stated 

 to exist between Monocotyledons and Dicotyledons cannot 

 be maintained as regards this family. On the other hand, 

 the trunk of the Cycas is frequently stunted to such a degree 

 that its transverse diameter is almost equal to its length. The 

 annual elongation is so small that scarcely any distinct inter- 

 nodes are observed between either the bud-scales or the fan- 

 like tufts of leaves, and the whole surface of the stem appears 

 closely imbricated with the remains of the dry scales and 

 leaves. Exactly the same formation, with the exception of 

 the texture of the wood, obtains in several of the Conifers, in 



