FORMATION OF BUDS. 209 



that is the formation of lateral buds in the substance 

 of the cambium, and that the shoots from those buds 

 should contain pith, in the same manner as the shoots 

 produced by the terminal buds upon the twigs, in which 

 there is a connection with the pith of the former year ; 

 but as the terminal bud is not at all developed so long 

 as the year's shoot is in vigorous growth, and makes 

 its appearance only when that is suspended, there is 

 no reason why a temporary suspension of the action of 

 the surfaces of the liber and alburnum should not oc- 

 casion the development of a bud there, in those trees 

 which have anastomosing rays that proceed outwards 

 from the centre. A diminution of the resistance of the 

 bark will occasion the appearance of a bud upon the 

 stem of a tree : an accidental wound in the bark of a 

 pear tree, through the greater part of the cortical 

 layers, but not through the liber, produced, in the 

 course of the same season, a tubercle of wood, covered 

 with epidermis, and rising above the surface of the old 

 bark : and next year the tubercle put out three or four 

 buds. 



Considering the beauty and the usefulness of trees 

 and other vegetables, it is, at first sight, rather singular 

 that so little should be known about their physiology. 

 One cause is, no doubt, the difficulty of the subject 

 itself ; and another is the disposition that we have to 

 localize the principle of life, by accounting some parts 

 vital and others not. There are great differences of 

 plants ; but in the active parts they are vital all over, 

 and admit of much .more division without the loss of 

 vitality, than even those animals that have the least 

 T 2 



