124 



plants is classed by phytologists among the conservative 

 organs. It is the part of the tree, in which its bulk and 

 strength principally reside, and has been represented by Lin- 

 naeus, as the Caudex ascendeiis, or root above ground ; an 

 illustration, as Keith truly observes, more fanciful than phi- 

 losophical.* 



The stems of trees are augmented in width by an annual 

 layer, and in length by an annual shoot, springing from the 

 terminating bud. The development of the shoot from the 

 stem is not effected in the same manner as that of the root, 

 by additions to the extremity only, but by the introsusception 

 of additional particles, throughout its whole extent, at least 

 in its soft and succulent state. The extension of the shoot, 

 as Du Hamel justly remarks, is inversely as its induration, 

 rapid while it remains herbaceous, but slow as it is converted 

 into wood. Hence, moisture and shade are the circumstances 

 of all others the most favourable to elongation, because they 

 prevent induration, or retard it.t In close and confined 

 plantations, therefore, where the external conditions of air 

 and light are imperfectly supplied, the roots are correlatively 

 proportional to the system of ramification. Trees so circum- 

 stanced push upwards to the light ; and from the warmth, 

 which their situation affords, their stems being thin and 

 slender in proportion to their height, they are destitute of 

 strength to resist the winds. The natural consequence is, 

 that their roots are extremely apt to be shaken and displaced 

 in the ground, and prevented from seeking proper food for 

 the branches, and other parts of the tree. 



Now, it is obvious, that it is these very properties, which 

 are the least adapted to removal. Nothing but a stem stout 

 and vigorous, and nourished by adequate side-branches, can 

 obviate the evils above delineated. Supports or props, 



• Physiolog. Bot. Vol. I. p. 43. f Physiolog. Bot. Vol. II. pp. 251, 

 252.— Kieser, Organ, des Plantes, p. 164. Also p. 166—168. 



