GROWTH OF STEMS 
265 
terminal bud gives the excurrent (Latin, ex, out; curro, 
to run) trunk of the evergreen trees, and a number of terminal 
buds of equal strength give the deliquescent (Latin, de, 
from; liquescere, to become liquid) branching of the elm 
and other trees. Between these extremes there are many 
intermediate forms. The buds for next season’s leaves are 
formed very soon after the leaves have reached their full 
size in the spring. Buds are protected in winter by coverings 
of scales which prevent them from becoming dry. A bud 
may contain leaves only, 
or flowers only, or both. 
Small markings on the 
smooth bark are lenticels, 
spots where the outer 
layer of the branch is 
broken, allowing air to 
enter the inner portions. 
232. Growth of Stems. 
— Most woody plants 
grow rapidly in the spring 
and early part of summer, Figure 253. — Elms. 
after which they cease in- Note the lack of a strong central stem 
creasing in size but con- and the repeated dividing of the branches, 
tinue to add material illustrating the deliquescent stem. 
which makes wood, thus enabling the stems to resist killing 
in the winter. Such plants are said to have a definite annual 
growth. This is illustrated by most woody trees. Other 
plants continue to grow until the end of the season. The 
latest formed wood in such plants is usually killed by the 
frost, with the buds on it. The plant begins to grow next 
season from axillary buds below the point where it was killed. 
Such plants are said to have indefinite annual growth. Ex¬ 
amples are red raspberry and sumac. Advantages of definite 
annual growth are twofold: (1) it enables a tree to grow 
very rapidly in the spring when conditions are most favorable 
