USES OF THE PHOTOSYNTHETIC FOOD 273 
to catching insects. Plants with such leaves are often called 
“carnivorous plants” or “‘insectivorous plants.’’ The “ Pitcher 
Plants’ are so named because the leaves form tubes of urns of 
various forms, which contain water, and to these pitchers insects 
are attracted and then drowned. (Fig. 245.) The plants known 
as “‘Sundews”’ have their leaves spread on the ground and 
clothed with secreting hairs. 
(Fig. 246.) These  secre- 
tions not only entangle in- 
sects but digest them. In 
the ‘‘Venus Flytrap,’ por- 
tions of the leaves work like 
steel traps and hold the in- 
sects fast until digested. 
(Fig. 247.) 
Uses of the Photosynthetic 
Food 
In plants, as in animals, 
the chemical processes upon 
which growth and other vital 
activities depend are both 
constructive and destruc- 
tive. While the simpler ele- : _ 
ments are being transformed Fic. 247.—Venus Flytrap, showing 
into complex substances, the leaves which open and close in catch- 
complex substances through oli 
respiration and other destructive processes are being broken into 
simpler substances. These chemical transformations constitute 
metabolism, and are said to be anabolic when constructive and 
catabolic when destructive. Through the plant’s metabolic 
processes numerous substances are formed, of which protoplasm, 
proteins, sugars, starches, fats, oils, hemicellulose, amino-com- 
pounds, cellulose, wood, cutin, suberin, enzymes, acids, tannins, 
glucosides, and alkaloids are common ones. All of these sub- 
stances are thought to be of some use to the plant, although the 
exact function of some of them is not definitely known. 
The photosynthetic grape sugar, since there is much evidence 
that in most cases it is the chief food formed by photosynthesis, 
may be regarded as a foundational food; for the photosynthetic 
