NOTE.--This is a good time to impress the fact that plants are the source of starch for manufacturing purposes. In England, potatoes are largely used; in Canada, corn. It will be interesting to state that the early settlers obtained their starch for laundry purposes at home from potatoes, by chopping or grinding them. The insolubility of starch in cold liquids may be effectively reviewed at this part of the lesson. The starch has been lying in the water of the potato cells for several months, yet has not dissolved. Let two or three of the class gradually heat the potato juice with its starch sediment, stirring all the time to distribute the sediment evenly. They will find that a little less than boiling temperature dissolves the starch. This will show them that heat is necessary for the solution of starch, and a heat much greater than that in the body, hence raw starch is indigestible. Recall the milk lesson and the uselessness of starch as a component of milk, unless the milk be cooked. Squeeze the juice from a sour apple or lemon, and note the taste. Explain that all fruit juices contain more or less acid. The effects of this acid in the body are similar to those of mineral matter. Protein is also found in plant juices; but in such small quantities that it may be disregarded as a source of food supply. GENERAL COMPOSITION OF PLANT JUICE Water; mineral matter; flavouring matter; starch or sugar, or both; acid (in fruit juice). LESSON III COMPOSITION OF SOLID MATERIAL IN CELLS OF SEEDS This part of the lesson may be developed as follows: 1. Seeds contain the building material for new plants, as well as their food for a short time. 2. Plants and animals require much the same material to build and feed them. 3. Animals require water, mineral matter, protein, sugar, starch, and fat. 4. Plants require the same; but the seed being a storehouse part of the plant, it will not have sugar, and water has to be supplied when the new plant is to be formed. 5. Seeds contain, therefore, mineral matter, protein, starch, and fat. NOTE 1.--Seeds will grow in water until their stored food is used: they must then be planted in soil, to get further nourishment. NOTE 2.--The two fuel foods, starch and fat, are not found together in abundance in seeds; one or the other will be much in excess. For instance, in walnuts there is a great deal of fat, while in peas and beans there is scarcely a trace of fat, but the starch is abundant. COMPARATIVE FOOD VALUE OF DIFFERENT PARTS OF PLANTS