BUDS AND BRANCHES 
103 
96. The record borne by the twig. In most cases the twig 
bears upon its surface and in its rings of wood a fairly com- 
plete record of the most important events of its life (fig. 90). 
Some of the markings on the surface of a 
twig which enable us to make out its his- 
tory are (1) bud-scale scars (from leat buds), 
(2) fruit scars, (3) leaf scars. Other mark- 
ings are found which tell less of the life 
history of the twig than those just enumer- 
ated, but which should also be considered, 
namely, (+) lenticels. 
The bud-scale scars, as the name implies, 
are the markings (figs. 86 and 88, 8. sc) left 
by the falling of the scales when the bud 
opened. Plants like geraniums, with naked 
buds, do not show such scars. .As the twig 
or branch in most cases is prolonged by the 
growth, spring after spring, of its terminal 
bud, each ring of scars marks the beginning 
of a new season’s growth. In many trees it 
is easy to determine the age of twigs or 
branches by counting the number of such 
rings (fig. 89). The distance between the 
tings of scars depends upon the rate of 
lengthwise growth of the shoot; this varies 
all the way from a fraction of an inch to 
ten feet or more per year. 
1. How many times greater was the rate 
of growth of the central twig in figure 88 
than the average yearly rate of figure 89? 
2. What was the cause of this rapid 
growth? (Examine a horse-chestnut tree.) 
Fic. 89. A slowly 
grown twig of horse- 
chestnut in winter 
condition 
d, dormant buds; fs, 
flower-cluster scar. 
The internodes are 
numbered in succes- 
sion (beginning at 
the bottom) with the 
respective years dur- 
ing which they were 
formed. One third 
natural size 
3. If the twig in figure 89 grew unequally in different 
years, what is a probable cause of the fact ? 
4. How did the leaves of figure 88 compare in size with 
those of figure 89? Why? 
