17G BOARD OF AGRICULTURE. 



t 



leaves at the same time as the other lilacs aud continued to 

 flourish till autumn. After the fall of the leaves, another one 

 was cut for examination, and it was found that a second layer 

 of wood and bark had formed as far down the stem as the 

 wire, where it was somewhat enlarged, and that no growth 

 whatever had taken place below this point. In the spring of 

 the third year, 1847, when the lilac buds began to swell and 

 the foliage to develop, the buds on the third specimen which 

 had been selected for experiment suddenly withered, although 

 they had appeared as plump as usual up to this time. In 

 June, 1847, this shoot was cut aud examined. The wood 

 below the ligature appeared brown and dead, and had received 

 no addition the previous year, while the part above the wire 

 was fresh and green and had formed a new layer of wood and 

 bark the preceding season. 



This seems to demonstrate that the cambium layer is the 

 seat of life, -and that whenever the direct communication 

 between the root and the foliage is cut off in this layer during 

 one entire season of growth, the whole plant perishes. 



It has also been determined by experiment that if several 

 rings of bark be removed from a growing shoot in such a 

 manner that on one of the isolated sections of bark there be 

 no leaf, while leaves remain on others above and below this, 

 then the leafless section will fail to make any growth in any 

 part. All the other sections, if furnished with one or more 

 healthy leaves, will increase in thickness by the formation of 

 new layers of wood and bark. This again seems to prove 

 that the material for growth is elaborated by the leaves and 

 is tralismitted only through the cambium and has no power of 

 penetrating the tissues of the Avood. 



The peculiar vital and organific po*ver of the cambium is 

 remarkably illustrated in the structure and growth of grafted 

 trees. Every person is aware that pear-trees are grown upon 

 quince-roots, and that they often bear finer fruit than when 

 cultivated as standards. This is doubtless owing to the fact 

 that quince-roots, being diminutive, furnish less water to the 

 leaves, Avhich thus elaborate a richer sap and produce more 

 perfectly developed wood and fruit. 



.The apricot may be grafted on the plum, and the peach on 

 the apricot, and the almond on the peach, and thus we may 



