CELL CONTENTS 183 
In powdered leaves, stems, etc., the chlorophyll grains occur 
in the cells as greenish, more or less structureless masses. Yet 
cells with chlorophyll are readily distinguished from cells with 
other cell contents. In witch-hazel leaf the chlorophyll grains 
appear brownish in color. Powdered leaves and herbs are 
readily distinguished from bark, wood, root, and flower powders. 
Leaves and the stems of herbs are of a bright-green color. 
With the exception of the guard cells, the chloroplasts occur one 
or more layers below the epidermis; but, owing to the trans- 
lucent nature of the outer walls of these cells, the outer cells of 
leaves and stems appear green. 
Wild cherry, sweet birch, and, in fact, most trees witn smooth 
barks have chloroplasts in several of the outer layers of the 
cortical parenchyma. When the thin outer bark is removed 
from these plants, the Dae layers are seen to be of a 
bright-green color. 
LEUCOPLASTIDS 
Leucoplastids, or colorless plastids, occur in the underground 
portions of the plant; they may, when these organs in which 
they occur are exposed to light, change to chloroplastids. 
Leucoplasts are the builders of starch grains. They take 
the chemical substance starch and build or mould it into starch 
grains, storage starch, or reserve starch. 
Other characteristic chromoplasts found in plants are yellow 
and red. Yellow chromoplasts occur in carrot root and nas- 
turtium flower petals. Red plastids occur in the ripe fruit of 
capsicum. 
STARCH GRAINS 
The chemical substance starch (CsHi00;) is formed in chloro- 
plasts. The starch thus formed is removed from the chloro- 
plasts to other parts of the plant because it is the function of 
the chloroplasts to manufacture and not to store starch. 
The starch formed by the chloroplasts is acted upon by a 
ferment which adds one molecule of water to CsHwO;, thus 
forming sugar CsHi.0.s. This sugar is readily soluble in the 
