OCR Text |
Show Why the Tree Leaves ' Turn Red When Chilly Autumn Days Return An examination of the withered leaves of the autumn foliage at the time of their turning red shows that they contain more . sugar and less starch than in midsummer. Leaves of evergreens, however, lose their red tints with the return of the warm season, sea-son, and reassume their green color. In these plants i. e., the holly and ivy the sugar of the leaf is transformed into starch in springtime. From these observations two inferences can be drawn first, that the red coloring substances sub-stances are probably of the nature of the glucoses, being in most cases compounds com-pounds of tannic substances with sugar; su-gar; secoDd, the chief physical conditions condi-tions for the formation of the red color are sunshine, which, on the one hand, enhances the assimilation and production' produc-tion' of sugar, and, on the other hand, quickens the chemical process that leads to the formation of the coloring matter, and, furthermore, a low temperature, tem-perature, which prevents the transformation trans-formation of the sugar into starch. In ether words, the red tints of autumn are the direct product of the meteorological meteor-ological conditions prevailing during that season i. e., sunshine and low temperature. |