
98 A TEXTBOOK OF GENERAL BOTANY 
grasses a group of cells just above each node remains meri- 
stematic for a considerable period of time and by division forms 
new cells, thus increasing the length of the internode. When 
the growing stem of a grass is pulled apart, it will usually break 
just above a node, where the soft meristematic tissue is located. 
This meristematic tissue in the grasses does not usually have 
enough strength to support the stem but 
is reénforced by the sheathing leaf bases 
(Fig. 68). This is evident when these leaf 
bases are removed, as the young stem will 
bend in the region of meristematic tissue. 
Even where intercalary growth is found it is 
not so important as apical growth, for apical 
growth produces new nodes and internodes, 
while intercalary growth only increases the 
length of the nodes to a limited extent. 
Position of leaves. Leaves are formed 
only at the tip of a stem. They grow to 
mature size, perform their functions for a 
time, and finally fall from the stem. As no 
new leaves are formed on the older parts of 
a stem, the old portions of branches are 
Foe Bi ane Poy leafless, the leaves being confined 
axils of leaves of mul. © the smaller and younger portions. When 
berry (Morus alba) leaves appear, on superficial observation, to 
Thedotsonthestemare 2!18¢ directly from large trunks or branches, 
lenticels. (x 2)” they really occur on short branches that are 
too small to be conspicuous. 
Leaf scars. When leaves fall, they leave scars, known as leaf 
scars (Fig. 94), on the stem. These scars persist for a consider- 
able length of time and mark the location of the nodes long after 
the leaves have fallen. In each scar are a number of more or less 
conspicuous dots, which in each species are arranged in a definite 
pattern. These dots mark the places where groups of xylem and 
phloém cells (called vascular bundles) passed from the stem to 
the leaf. 

