. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. 514 AMERICAN JOURNAL OF BOTANY [Vol. 25, modia when they are continuously exposed. The cultures exi)osed to light from a lOO-watt bulb for eight hours per day required only one or two days longer for fruiting than cultures continuously ex- ])osed, whereas, if a direct mathematical relationship existed, theoretically they would require thirty-three days, since they were exi)osed to light only one-third of the time. What actually occurred was that cul- tures continuo
. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. 514 AMERICAN JOURNAL OF BOTANY [Vol. 25, modia when they are continuously exposed. The cultures exi)osed to light from a lOO-watt bulb for eight hours per day required only one or two days longer for fruiting than cultures continuously ex- ])osed, whereas, if a direct mathematical relationship existed, theoretically they would require thirty-three days, since they were exi)osed to light only one-third of the time. What actually occurred was that cul- tures continuously exposed recjuired a total of 2(54 hours exposure to light for fruiting, while cultures e\j)osed eight hours i)er day reciuired only 90 to 104 hours of exi)osure, although they did spend a longer time in the vegetative phase than cultures contin- uously exposed. Table 2. L'Kjht trans?)! analyses of colored plates. Plato used 400 Wave length (milliinicrons) 450 500 550 603 650 703 Blue . Rod .. Yollow Experiments relative to the effect of lights of vari- ous wave lengths (of the visible si)ectrum) were first contlucted with moist chamber cultures which were continuously exposed to lights transmitted through colored glass i)lates. One series was conducted, and then standardized gelatin filters were substituted for the plates. In the original experiment three colored i)lates were used: red, blue, and yellow. These i)lates were analyzed by means of a Razek- Mulder Color Analyzer; results of the light trans- mission analyses are sununarized in table 2. From this table it may be seen that the blue ])late pa.'^.sed a comi)aratively high i)ercentage of light in the violet and blue bands of the spectrum, very little in the green and yellow, practically none in the orange, but 3. Summary of results of one experiment imng lii/ht transmitted thr(ti((/
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