the seeds in three classes, 1. Much starch (colour blackish or purple), 2. Little starch (pale blue or greenish), 3. No starch (brown or yellow). =15.= _Rate of growth of seedlings as affected by differences in temperature._ Pack soft wet paper to the depth of an inch in the bottom of four glass bottles or tumblers. Put ten soaked peas or beans into each. Cover each securely and set them in places having different temperatures that vary little. (A furnace room, a room with a stove, a room without stove but reached by sunshine, an unheated room not reached by the sun). Take the temperatures occasionally with the thermometer to find difference in temperature. The tumblers in warm places should be covered very tightly to prevent the germination from being retarded by drying out. Record the number of seeds which sprout in each tumbler within 1 day, 2 days, 3 days, 4 days, etc. =16.= _Is air necessary for the germination and growth of seedlings?_ Place damp blotting paper in the bottom of a bottle and fill it three-fourths full of soaked seeds, and close it tightly with a rubber stopper or oiled cork. Prepare a “check experiment” by having another bottle with all conditions the same except that it is covered loosely that air may have access to it, and set the bottles side by side (why keep the bottles together?). Record results as in the preceding experiment. =17.= _What is the nature of the gas given off by germinating seeds?_ Fill a tin box or large-necked bottle with dry beans or peas, then add water; note how much they swell. Secure two fruit jars. Fill one of them a third full of beans and keep them moist. Allow the other to remain empty. In a day or two insert a lighted splinter or taper into each. In the empty jar the taper burns: it contains oxygen. In the seed jar the taper goes out: the air has been replaced by carbon dioxide. The air in the bottle may be tested for carbon dioxide by removing some of it with a rubber bulb attached to a glass tube (or a fountain-pen filler) and bubbling it through lime water. =18.= _Temperature._ Usually there is a perceptible rise in temperature in a mass of germinating seeds. This rise may be tested with a thermometer. =19.= _Interior of seeds._ Soak seeds for twenty-four hours and remove the coat. Distinguish the embryo from the endosperm. Test with iodine. =20.= _Of what utility is the food in seeds?_ Soak some grains of corn overnight and remove the endosperm, being careful not to injure the fleshy cotyledon. Plant the incomplete and also some complete grains in moist sawdust and measure their growth at intervals. (Boiling the sawdust will destroy moulds and bacteria which might interfere with the experiment.) Peas or beans may be sprouted on damp blotting paper; the cotyledons of one may be removed, and this with a normal seed equally advanced in germination may be placed