CELL INCLUSIONS 13 
stained with carotin. Examine also the red cells of a ripe 
tomato or the yellow cells of a petal of nasturtium (Tropaeo- 
lum) or the cells of rose hips. 
22. Cell Inclusions. Within many cells are often 
found bodies not living and not an essential part of the 
cell but which have been produced by the cell itself. 
They may be temporary or permanent. They may lie 
in the cytoplasm, in the vacuoles or in the plastids. 
Such bodies are called cell inclusions. The most fre- 
quent cell inclusions are starch, aleuron, crystals and 
sometimes drops of fat or oil. 
°23. Starch. In the green cells of many plants there 
are produced in the chloroplasts on exposure to light 
‘small pearly white grains of starch. 
These are usually transformed into 
sugar during the night and used by the 
plant for food or transported to some 
other part such as root, tuber or seed, 
where the sugar may be again con- 
verted to starch, in the leucoplasts, to... 4 —starch 
remain until needed by the plant for sr3ins (lange) and 
food. Whereas in the green cells of 
a leaf the starch does not ordinarily accumulate in great 
quantities, the storage cells of a plant become so packed 
with it sometimes that little else can be seen. 
Starch is a carbohydrate and is closely related chemi- 
cally to cellulose and to the sugars. It is composed of 
carbon, hydrogen and oxygen in the proportions indi- 
cated by the formula (CgHi00;5)n, in which “n” is a 
fairly high but not exactly ascertained amount. By the 
action of certain organic substances produced by the cell 
and called enzymes, or of some of the acids and heat, it 
ean be converted into some forms of sugar. 
Starch grains frequently show a concentric structure, 
