. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 78 BOTANY the proper stimuli are applied to it, start in its growth into a new plant. Let us see what these stimuli are. Effect of Water on Dry Seeds. — Weigh ten dry navy beans; leave them in water over night; reweigh. How much have they increased in weight? We have already found that water gets into the seed through the micropyle. It can be proved that it gets in through the seed coat as well. If you cover five seeds entirely with paraffin, and in five others cover the hilum, micropyle, a
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 78 BOTANY the proper stimuli are applied to it, start in its growth into a new plant. Let us see what these stimuli are. Effect of Water on Dry Seeds. — Weigh ten dry navy beans; leave them in water over night; reweigh. How much have they increased in weight? We have already found that water gets into the seed through the micropyle. It can be proved that it gets in through the seed coat as well. If you cover five seeds entirely with paraffin, and in five others cover the hilum, micropyle, and half of the remainder of the coat, a difference in weight and size will be apparent the next morning. Expansive Force of Germinating Seeds. — The expansive force of germinat- ing seeds is considerable. You have noticed that the bean is considerably larger after soaking. Fill a small bottle almost full of dry seeds (beans or peas), then fill the space left with water; wire in the cork tightly. Leave the bottle overnight and note the results next morn- ing. Would this force be of use in getting a start under the soil ? Have you noticed that the soil is lifted in the garden by the rows of germinating peas and beans just before they come up ? Is this due entirely to the expansive force of seeds ? Watch future experiments before you attempt a definite an- swer. Will a Dry Seed germinate?— Place a layer of moist blotting paper or sawdust in bottom of each of three cups or three tin cans. Soak fifteen navy beans overnight. Place five in each dish. Water one dish so as to cover the seeds; water the second so as to keep sawdust rather moist; let the third remain unwatered. Cover the cups with loose-fitting covers. Make daily observations of the number germinating, and the con- dition of each for at least ten days. Put the results in tabular form. What amount of water is most favorable for germination of the navy bean ? * Water a Factor in Germination. — A dry seed will not ge
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