106 GROWTH OF LEAF-BUDS. 
temporary duration, falling off as soon as the growth of the bud 
commences in the spring. 
The bud thus contains all the elements of a stem or 
branch ; in fact it is really the first stage in the development 
of these parts, the axis being here so short that the rudimentary 
leaves are closely packed together, and thus overlap one an- 
other. When growth commences in the spring, or whenever 
vegetation is reanimated, the internodes between the leaves be- 
come developed (jig. 208, d, d, d), and these therefore become 
separated from one another, c, c, c, and thus the stem or branch 
increases in length, or a new branch isformed. In other words, 
the leaves, which in a bud state overlap one another and sur- 
round a growing point or axis, by the elongation of the inter- 
nodes of that axis become separated and dispersed over a branch 
or an elongation of the stem, much in the same way as the 
joints of a telescope become separated from one another by 
lengths of tube when it is drawn out. The branch, therefore, 
like the bud from which it is formed, necessarily contains the 
same parts as the axis upon which it is placed, and these parts 
are also continuous with that axis, with the exception of the 
pith, which, although originally continuous in the bud state, 
ultimately becomes separated by the development of tissue at 
the point where the branch springs from the axis. But when 
a branch becomes broken off close to the wood, and there are 
no buds upon it to continue its growth, it becomes ultimately 
enclosed by the successive annual layers of wood, and thus a 
knot is formed. 
From the above circumstances it follows that a bud resembles 
in its functions the embryo from which growth first commenced, 
and it has accordingly been termed a fixedembryo. There is this 
difference, however, between them :—a bud continues the in- 
dividual, while the embryo continues the species. A stem is 
therefore really made up of a number of similar parts or buds, 
called phytons, which are developed in succession, one upon the 
summit of the other. Hence, by the development of a terminal 
bud, the stem increases in height ; and by those situated late- 
rally branches are produced. A tree may thus be considered as 
a compound body, formed of a series of individuals which mu- 
tually assist one another, and benefit the whole mass to which 
they belong. In Dicotyledonous trees, which form lateral or 
axillary buds, the destruction of a few branches is of no con- 
sequence, as they are soon replaced ; but in Palms, and most 
other monocotyledonous trees, and also in those of Cormophytes, 
which develop only from terminal buds, the destruction of these 
under ordinary circumstances, as we have seen (pages 99 and 
103), leads to their death. 
The buds or similar parts, of which a tree, or other Dicotyle- 
donous plant, may thus be shown to be made up, being thus 
distinct individuals, as it were, in themselves, are also capable 
