AUTUMN TINTS

Nelson Evening Mail, Volume LXIII, 21 November 1928, Page 3

AUTUMN TINTS

WHY LEAVES CHANGE COLOUR

Tho glowing colours trees wear in autumn are the outcome of economic chemical changes which are being carried on in tho leaves. Trees are green because they must manufacture from the air and the' sunshine the food for their life. No plant can make this green stuff, which is called chlorophyll, if it is totally deprived of iron. Every plant and every tree must suck up from the. earth in its sap solbue iron. Besides iron, a certain degree of warmth is necessary for the formation of the green chlorophyll of tho leaf, and when tho temperature falls in autumn tho colouring matter ceases to function. Leaves are no longer necessary, and beneo they fall. Before they fall every particle of food that has been made is drained away. Tho chlorophyll, together with sugar and other complex material, is dissolved in the sap, and recedes into tho stem and roots, to bo stored there for tho winter months. When tho green matter has disappeared the leaf assumes various tints —brownish yellow, brownish red,- vivid crimson, purplish red, and so on, according to its species. These colours are produced by wasto products formed in "the leaf during the disorganisation of its tissues. Finally the bark of the twig closes up right across tho stem of the loaf, which is gently but firmly deprived of its grip. Anyone who looks closely afc fallen leaves will see here and there somo traces of tho iron that helped to paint the trees with the glorious tawny hues of autumn. BIRD BUILDERS Few people think of the nightingale as a. basket maker, but practically all our. songsters use wonderfully-twined twigs for their nests. Birds skilled in the craft are the missel-thrush, tho jay, the bullfinch, and the reed-warbler. The swallow and kouse-martin are, of course, masons. The nuthatch performs similar work in old trees, besides adding carpentry to its other accomplishments. The linnet and tho greenfinch not only use moss, wool and hair for tho interior of their nests, but make tho outside of roots and twigs, so manipulated as to form perfect exampFes of tho art of basket-weaving.