Footnotes 6 and 7: Directions for making these solutions will be found in Hunter's _Laboratory Problems in Civic Biology_. Starch changed to Grape Sugar in the Corn.--That starch is being changed to grape sugar in the germinating corn grain can easily be shown if we cut lengthwise through the embryos of half a dozen grains of corn that have just begun to germinate, place them in a test tube with some Fehling's solution, and heat almost to the boiling point. They will be found to give a reaction showing the presence of sugar along the edge of the cotyledon and between it and the endosperm. Digestion.--This change of starch to grape sugar in the corn is a process of _digestion_. If you chew a bit of unsweetened cracker in the mouth for a little time, it will begin to taste sweet, and if the chewed cracker, which we know contains starch, is tested with Fehling's solution, some of the starch will be found to have changed to grape sugar. Here, again, a process of digestion has taken place. In both the corn and in the mouth, the change is brought about by the action of peculiar substances known as digestive ferments, or _enzymes_. Such substances have the power under certain conditions to change insoluble foods--solids--into soluble substances--liquids. The result is that substances which before digestion would not dissolve in water now will dissolve. [Illustration: A germinating corn grain. _C_, cotyledon; _H_, growing root (_hypocotyl_); _P_, growing stem (_plumule_); _S_, endosperm; _d.s._, digested starch; _p.r._, primary root; _s.r._, secondary root; _r.h._, root hairs.] The Action of Diastase on Starch.--The enzyme found in the cotyledon of the corn, which changes starch to grape sugar, is called _diastase_. It may be separated from the cotyledon and used in the form of a powder. To a little starch in half a cup of water we add a very little (1 gram) of diastase and put the vessel containing the mixture in a warm place, where the temperature will remain nearly constant at about 98 deg. Fahrenheit. On testing part of the contents at the end of half an hour, and the remainder the next morning, for starch and for grape sugar, we find from the morning test that the starch has been almost completely changed to grape sugar. Starch and warm water alone under similar conditions will not react to the test for grape sugar. Digestion has the Same Purpose in Plants and Animals.--In our own bodies we know that solid foods taken into the mouth are broken up by the teeth and moistened by saliva. If we could follow that food, we would find that eventually it became part of the blood. It was made soluble by digestion, and in a liquid form was able to reach the blood. Once a part of the body, the food is used either to release energy or to build up the body. Summary.--We have seen: 1. That seeds, in order to grow, must possess a food supply either in or around their bodies.