56 THE VEGETABLE WORLD. 
buds: they present themselves on all parts of the vegetable, now 
upon the stem, the leaves, the flowers, and the roots. The root of 
the Sumac, or Stag’s-horn-tree of Virginia (Rhus Cotinus), for 
example ; of the Dutch Poplar or Pollard Willow (Salix Alba) ; of 
the common Acacia, and many others, run horizontally in the soil 
very near the surface, producing adventitious buds, which root 
themselves rapidly, and rapidly multiply the plant, so that in a few 
years they become a considerable nuisance. 
The formation of adventitious buds is frequently produced by 
accidental irritation. The wheel of a cart, for instance, grazes the 
; or the root of a tree is wounded by the passing plough- 
share, and an adventitious bud results. If we cut down the head 
of a group of forest trees; the plants which, left to themselves, 
would have become stately trees, are transformed into stunted groups 
which cover themselves afterwards with branches, all of the same 
age and the same strength; they have been transformed from trees 
of stately growth to pollarded dwarfs. In the case of the Willow, 
this principle of adventititious budding has been largely utilised. 
Willows of enormous trunks, but short and deformed, surmounted 
by a thick tuft of branches, as in the engraving at the head of this 4 
chapter, are commonly known as pollards, and owe their singular 
appearance to the regular and periodical cutting to which they are 
subjected. In consequence of this mutilation, a great number of 4 
adventitious shoots are formed, which subsequently produce sO 
many branches of like size. These branches are cut to make — ' 
supports for young trees, for pea-sticks in horticultural districts, 
and as props for the vine in wine-producing countries. In Epping 4 
Forest, in the neighbourhood of London, it has been the custom 
from time immemorial to have annual sales of these cuttings, at 
which the neighbouring inhabitants are supplied with wood both 
for firing and horticultural purposes. 
When the Poplar-tree of Italy (Populus fastignatis) reaches 
twenty-five or thirty years, it is cut down, when it forms planks 
of some value ; but it is also pruned every five years, the result of 
pruning being numerous adventitious buds, which produce branches 
much used for fences and for fire-wood, 
Buds are placed upon the stem at regulated intervals, where q 
oe em Pee 
Af. were 
