Page:Popular Science Monthly Volume 57.djvu/527

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he facts and considerations we have passed in review fairly indicate the physiological and psychological preëminence of red among the colors of the spectrum to which we are sensitive. What is the cause of that preëminence?

It seems to me that two orders of causes have coöperated to produce this predominant influence, one physical and depending on the special effects of the long-waved portion of the spectrum on living matter, the other psychological and resulting from the special environmental influences to which man, and to some extent even the higher animals generally, have been subjected. It is possible that these two influences blend together and cannot at any point be disentangled; it is possible that acquired aptitude may be inherited or that what seem to be acquired aptitudes are really perpetuated congenital variations; but on the whole the two influences are so distinct that we may deal with them separately.

On the physical side the influence of the red rays, although there is much evidence showing that it may be traced throughout the whole of organic nature, is certainly most strongly and convincingly exhibited on plants. The characteristic greenness of vegetation alone bears witness to this fact. The red rays are life to the chlorophyll-bearing plant, the violet rays are death. A meadow, it has been justly said, is a vast field of tongues of fire greedily licking up the red rays and vomiting forth the poisonous bile of blue and yellow. An experiment of Flammarion's has beautifully shown the widely different reaction of plants to the red and violet rays. At the climatological station at Juvisy he constructed four greenhouses—one of ordinary transparent glass, another of red glass, another of green, the fourth of dark blue. The glass was monochromatic, as carefully tested by the spectroscope, and dark blue was used instead of violet because it was impossible to obtain a perfect violet glass. These were all placed under uniform meteorological and other conditions, and from certain plants such as the sensitive plant, previously sown on the same day in the same soil, eight of each kind were selected, all measuring 27 millimetres, and placed by two and two in the four greenhouses on the 4th of July. On the 15th of August there were notable differences in height, color and sensitiveness, and these differences continued to become marked; photographs of the