THE STEM 109 
little sugar, especially when new, or when it is 
beginning to shoot, and soluble carbohydrates are 
required. In the Jerusalem artichoke, another tuber, 
we again find inulin, though sugar, too, is always 
present. The reserve material of stems is accumulated 
during one year to nourish the young shoot of the 
next. 
In Leaves.—In the fieshy leaf bases of bulbs carbo- 
hydrate is present. The onion, for instance, shows a 
ecopions supply of sugar. In the onion, which is a 
biennial, this sugar is for the production of flower and 
fruit in the second year. In the bulbs of the lily and 
nareissus, however, the reserve merely supplies the 
young shoot till it can gather food for itself and return 
what it has borrowed from the store below. 
Fruits, like the apple, cherry, and blackberry, have 
sugary flesh which, forming the food of birds and 
other animals, provides for the distribution of the 
seed. In cases moreover where the fruit falls naturally 
to the ground, the fleshy material rots and forms a 
supply of humus that the young seedling can use as 
soon as its roots are established. 
SUMMARY. 
Stems conduct inorganic materials to and organic 
materials from the leaves, and serve to spread out the 
leaves and display the flower and fruit. A dicotyledon 
has epidermis to protect; cortex to conduct carbo- 
hydrates from the leaves; a ring of medullary rays 
alternating with vascular bundles, the latter consisting 
of bast, to conduct proteins from the leaves; cambium 
to provide for growth, and wood to conduct water 
from the root; pith, and sometimes pith cavity in the 
middle. In older stems annual rings mark the differ- 
enee in growth of spring and autumn wood, pith 
disappears, cortex and bast form the inner bark, and 
the outer cortex forms eorky bark. In monocotyledons, 
