16 



THE MODERN PEACH PRUNER. 



terior layers are the latest deposited, and the 

 youngest. 



The ligneous body itself is composed of hard 

 wood or heart, and of alburnum or soft wood. 

 The Jieart, formed of the innermost layers, is 

 composed of tissue, which material deposits have 

 completely filled up. The alburnum, or recently- 

 formed ligneous substance, is situated between the 

 heart and the bark of the tree. The outer layers 

 contain the sap -vessels, which perform their im- 

 portant functions in proportion to their formation. 



The bark comprehends the liber, and the cor- 

 tical layers. The liber is the interior portion of 

 the bark, and covers the alburnum. The liber is 

 the seat of vitality in the tree. It is composed, 

 therefore, of a certain number of thin layers of 

 vessels, having their origin at the base of a leaf, 

 and their extremity at the spongioles. While, 

 however, in the ligneous body, the exterior layers 

 are the latest produced, in the liber, on the con- 

 trary, the newest are the innermost ones. The 

 cortical layers are those formed by the oldest ones 

 of the liber. In young subjects the liber is covered 

 with thin tissues, called respectively inner and outer 

 epidermis. 



The bud, situated at the axil of the leaves, is the 

 rudiment of the young shoot. It is formed by a 

 deviation of the vessels of the medullary canal. 



