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Page:Popular Science Monthly Volume 57.djvu/528

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518
POPULAR SCIENCE MONTHLY.

plants on the 4th of October showed that while those under blue glass had made no progress, those under red glass had attained extraordinary development, red light acting like a manure. While those under blue glass became insensitive, under red glass the sensitive plants had become excessively sensitive to the least breath. They also flowered, those under transparent glass being vigorous and showing buds, but not flowering. The foliage under red glass was very light, under blue darkest. Similar but less marked effects were found in the case of geraniums, strawberries, etc. The strawberries under blue glass were no more advanced in October than in May; though not growing old their life was little more than a sleep. It appears, however, that the stimulating influence of red light fails to influence favorably the ripening of fruit. Zacharewiez, professor of agriculture at Vaucluse, has found that red, or rather orange, produces the greatest amount of vegetation, while as regards fruit, the finest and earliest was grown under clear glass, violet glass, indeed, causing the amount of fruit to increase but at the expense of the quality.

Moreover, the lowest as well as the highest plants participated in this response to the red rays, and in even a more marked degree, for they perish altogether under the influence of the violet rays. Marshall Ward and others have shown that the blue, violet and ultra-violet rays, but no others, are deleterious to bacteria. Finsen has successfully made use of this fact in the treatment of bacterial skin diseases. Reynolds Green has shown that while the ultra-violet rays have a destructive influence on diastase, the red rays have a powerfully stimulating effect, increasing diastase and converting zymogen into diastase.

While the influence of the red rays on the plant is thus so enormous and easily demonstrated, the physical effects of red on animals seem to be even opposite in character, although results of experiments are somewhat contradictory. B├ęclard found that the larva? of the flesh fly raised under violet glass were three fourths larger than those raised under green glass; the order was violet, blue, red, yellow, white, green. In the case of tadpoles, Yung found that violet or blue was especially favorable to the growth of frogs; he also found that fish hatch most rapidly under violet light. Thus the influence that is practically death to plants is that most favorable to life in animals. Both effects, however, as Davenport truly remarks in his 'Experimental Morphology,' when summing up the results of investigations, are due to the same chemical metabolic changes, but while plants succumb to the influence of the violet rays, animals, being more highly organized, are able to take advantage of them and flourish.

At the same time the influence of violet rays on animal tissue is by no means invariably beneficial; they are often too powerful a stimulant. That the violet rays have an influence on the human skin which in the