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, strawber- 

 ries, 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 some- 

 Avhat contradictory. Beclard 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, how- 

 ever, 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 



