PROGRESS OF VEGETATION. 303 



injure both the growth and appearance of the trees. 

 These are very apt to appear on fruit trees, and in- 

 deed on all trees that are cultivated out of their 

 natural habits. But when the tree is uninjured, as it 

 has every chance of being in a seedling oak of the 

 first year, the whole tree soon comes into action; 

 the buds are expanded into leaves, and lengthened 

 into twigs. After the tree has begun to act, and 

 thence till the leaves have attained their full size, 

 the juice or sap of the tree is in the wood, and the 

 bark is comparatively dry. But after the leaves 

 have attained their full size, and are in complete ac- 

 tion, sap appears in the bark as well as the wood. 

 The sap which then appears is not however the 

 same as that which was in the wood before the 

 leaves came on. The air, heat, and light have all 

 had an influence upon it in the leaves, and fitted it 

 for the composition of the new substance. 



In the young shoots, those that have been pre- 

 pared the same season, the process is the same as it 

 was in the first oak ; but in the other parts, the pre- 

 pared juice spreads itself between the wood and the 

 bark. First in a state nearly fluid, but it gradually 

 becomes a little granular, then fibrous, and it ulti- 

 mately divides into wood and bark in the same manner 

 as that of the former year ; and when that has been 

 completely performed, the leaves are " healed off," 

 and the tree passes into its repose as before. The 

 result of the annual action has been to case the 

 former tree, roots, and all, with a new layer of wood 

 and bark, and to lengthen it by a twig at every bud. 

 If we could by any means separate the two trees by 

 pulling the first out of the second, as an instrument 

 is pulled out of its case, we should have a sight of 

 two years' progress of the oak, and only the leaves 

 would be wanting to give us the whole of what had 

 grown from the acorn during those years. 



The third and every succeeding year is merely a 

 repetition of what took place during the second, only 



