BUDS ON LEAVES. 37 



upon the stumps left when the wood is cut, of new shoots from the callus or from 

 the dormant eyes, shoots which in the course of thirty or forty years replace 

 the old plantation, that is to say, the mass of wood which has been taken away. 

 Pollarding is another instance. Pollard-trees are kept cut down to a particular 

 height, and in consequence become thickened at the top, as may be seen in the case 

 of Poplars, Ashes, and more particularly Willows. The pruning of Vines and Fruit- 

 trees is likewise of this category, and the same process is applied also to the woody 

 plants trained to form espaliers or hedges when a park is being laid down or an 

 estate inclosed. All these manipulations have in view, on the one hand, a develop- 

 ment of more vigorous shoots from the stumps that are left behind and the 

 acquisition of as abundant a yield of timber, forage, or fruit as possible; on the other 

 hand, a denser growth of the tree-top, or a stunting of the tree, such as is required 

 for gardens in the old French style, with their formal green walls, obelisks, and 

 marvellous ornamentation. Seeing, however, that each of the various trees and 

 shrubs has peculiarities of its own in relation to the formation of callus and 

 dormant eyes, many different modes of pruning are applied to them. We cannot 

 generalize from one case to all the rest, and it would be a great mistake, for 

 example, to try to pollard Apple-trees like Willows, or to convert Pines into under- 

 wood. Climatic conditions must also be taken into account in connection with 

 these intentional mutilations of cultivated plants. To give one instance of their 

 effect, it may be mentioned that vine-pruning in Hungarian vineyards is quite 

 different from the corresponding process employed on the Rhine, whilst the latter 

 again differs from the method practised in Northern Italy, which, in its turn, is not 

 the same as that of Southern Italy. In each locality the kind of treatment most 

 adapted to prevailing climatic conditions has been found out in course of time. 



BUDS ON LEAVES. 



Hitherto only such buds as are developed on roots or on the various regions 

 of the stem have been dealt with; but an enumeration of these does not nearly 

 exhaust the multiplicity of bud-forms which exist. Buds and shoots may also 

 spring from the tissues of leaves— particularly foliage-leaves. These are termed 

 epiphyllous buds or shoots, and they are classified in several groups according 

 to their places of origin. 



Before discussing this classification it is necessary to note carefully that 

 epiphyllous buds must be strictly distinguished from those which occur on the 

 foliage-leaves of Helwingia and on the leaf-like cladodes (or phylloclades) of 

 Butcher's-broom, &c. As regards Helwingia (see fig. 198) careful investigations 

 prove that certain strands proceed from the leaf -bearing axis to the buds seated 

 upon the leaves. Each of these strands represents a lateral axis, but instead of 

 being free it is bound up (or fused) with the midrib of the leaf from the axil 

 of which it springs. The lateral axis thus adnate to the midrib first abandons 

 its connection with the latter at a spot on the lamina, about a third of its entire 



