FLOWER-OARDENING. "135 



the one horizontal, the other upwards, and the third down 

 wards. 



93. The horizontal development is confined to the cellular 

 system of the bark, pith, and medullary rays. 



94. The upward and downward developments are confined 

 to the woody fibre and vascular tissue. 



95. In this respect they resemble seed ; from which they 

 differ physiologically in propagating the individual, while seed 

 can only propagate the species. 



96. When they disarticulate from the stem that bears them, 

 they are called Buds. 



97. In some plants, a bud, when separated from its stem, 

 will grow and form a new plant if placed in circumstances favor- 

 able to the preservation of its vital powers. 



98. But this property seems confined to plants having a firm, 

 woody, perennial stem. 



99. Such buds, when detached from their parent stem, send 

 roots downwards and a stem upwards. 



100. But if the buds are not separated from the plant to 

 which they belong, the matter they send downwards becomes 

 wood and liber (66), and the stems they send upwards become 

 branches. Hence it is said that wood and liber are formed by 

 the roots of leaf-buds. 



101. If no leaf-buds are called into action, there will be no 

 addition of wood; and, consequently, the destruction or ab- 

 sence of leaf-buds is accompanied by the absence of wood ; as 

 is proved by a shoot, the upper buds of which are destroyed 

 and the lower allowed to develop. The lower part of the 

 shoot will increase in diameter ; the upper will remain of its 

 original dimensions. 



102. The quantity of wood, therefore, depends upon the 

 quantity of leaf-buds that develop. 



103. It is of the greatest importance to bear this in mind in 

 pruning timber trees ; for excessive pruning must necessarily 

 be injurious to the quantity of produce. 



104. If a cutting with a leaf-bud on it be placed in circum- 



