CHAPTER VII 
SYNTHETIC TISSUE 
Under synthetic tissue are grouped all tissues and cells which. 
form substances or compounds other than protoplasm. Such 
compounds are stored either in special cavities or in the cells 
of the plant, as the glandular hairs; internal secreting cavities 
of barks, stems, leaves, fruits, seeds, and flowers; photosyn- 
thetic cells or cells with chlorophyll, and the parenchymatic 
cells which form starch, sugar, fats, alkaloids, etc. 
PHOTOSYNTHETIC TISSUE 
The most important non-glandular synthetic tissue is the 
photosynthetic tissue, which is composed of the chlorophyll- 
bearing cells of the plant. These are the so-called green cells 
of leaves, of stems of herbs, of young woody stems, and in the 
older woody stems of plants like wild cherry, birch, etc. The 
greater part of the tissue of leaves is composed of chlorophyll- 
bearing cells. 
Leaves collectively constitute the greatest synthetic manu- 
facturing plant in the world, because the green cells of the leaf 
produce most of the food of men and animals. The two com- 
pounds utilized in the manufacture of food are carbon dioxide 
(CO2) and water (H,O). These two compounds are combined 
by chlorophyll through the agency of light into starch. Chemi- 
cally this reaction may be expressed as follows: 
6CO, +- 5H:20 => 2C.HwO; -- 60>. 
During the day a large quantity of starch is formed. At 
night through the action of a ferment the excess of starch remain- 
ing in the leaf is converted into sugar (CgHi20¢) — CgHyO; + 
H.O = C,;H;.0¢. In this form it is distributed to the living 
cells of the plant. The presence or absence of starch in leaves 
is easily ascertained by placing the leaf in hot alcohol to remove: 
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