84 ELEMENTS OF BOTANY. 
Sometimes the tree fails altogether to produce buds at 
places where they would regularly occur. In the lilac the 
terminal bud usually fails to appear, and the result is constant 
forking of the branches. 
113. Adventitious Buds.— Buds which occur in irregular 
places, that is, not terminal nor in or near the axils of leaves, 
are called adventitious buds ; they may spring from the roots, 
as in the silver-leafed poplar, or from the sides of the trunk, 
as in our American elm. In 
many trees, for instance wil- 
lows and maples, they are 
sure to appear after the trees 
. have been cut back. Willows 
are thus cut back or pollarded, 
as shown in Fig. 62, in order 
to cause them to produce a 
large crop of slender twigs 
suitable for basket-making. 
Leaves rarely produce buds, 
but a few kinds do so when. 
they are injured; and those 
of the bryophyllum, a plant 
225 62. Ng as formed SIR Adven- maori ee nee 
titious Buds on Pollarded Willows. ever, almost always send out 
buds from the margin when 
they are removed from the plant while they are still green 
and fresh. 
‘114. Experiment 23.—Pin up a bryophyllum leaf on the wall 
of the room or lay it onthe surface of moist earth, and follow, day by 
day, the formation and development of the buds which it may produce. 
This plant seems to rely largely upon leaf-budding to 
reproduce itself, for in a moderately cool climate it rarely 
flowers or seeds, but drops its living leaves freely, and from 
each such leaf one or several new plants may be produced. 
