CONTROLLED ENVIRONMENTAL CONDITIONS 321 



temperature favors development of anthocyanin in the apple without a 

 change in sugar content. He also points out that the small amounts of this 

 pigment found in cells call for relatively little sugar as a building material 

 and concludes that low temperature probably acts directly rather than 

 through sugar accumulation. 



While fruits picked on August 25 showed rapid reaction to the optimum 

 light and temperature, the rate of coloring slowed down after the 25th of 

 August, whether the fruit remained on the tree or was picked. Living 

 skin taken from the apple and floated on water developed pigment as 

 readily as skin on the apple, but dead skin did not develop pigment. 

 Arthur believes the reason apples kept in storage until early November lose 

 the power to develop pigment is because the epidermal cells gradually die 

 during a month or more of storage. The cranberry and Abundance plum 

 capable of developing pigment in darkness developed it much more rapidly 

 if exposed to the most effective band of ultraviolet at 15° C (59° F). 



A State of Washington orchardist stated that if this process could be 

 developed for commercial application he would sell his orchards, because 

 high coloring is one of the big selling points of Washington apples. He is 

 probably in no danger, for it is expensive to expose all the surface of each 

 apple to the proper ultraviolet rays at 15° C (59° F) for about two days. 



Lojkin " exposed several kinds of green plants, both growing in soil and 

 detached from their roots, to several sources of ultraviolet rays to deter- 

 mine the rate of production of vitamin D within the plants. She also 

 exposed rats directly to the same ultraviolet sources to determine the length 

 of exposure necessary for complete antirachitic protection. 



Rats fed on the Sherman-Pappenheimer limited diet 84 needed 30 

 minutes' daily exposure to midday sunlight passing through an ultraviolet- 

 transmitting filter, designated as N, in order to give complete antirachitic 

 protection. During summer months 15 minutes of daily exposure is re- 

 quired. When this diet is supplemented by 5 grams of green lettuce per 

 rat per day, both the rate of growth and the needed exposure increase. 



When the mercury vapor lamp in quartz is used and the light is passed 

 through a filter designated as F, which is opaque to all rays shorter than 

 286 niju, only one minute's exposure is needed for complete protection. 

 The author concludes that the most effective rays in curing rickets are 

 within the limits of the solar spectrum at sea level, that is, 290 m/x or 

 longer, and that rays shorter than 286 mn have little or no antirachitic 

 action. 



Ultraviolet rays from the solar spectrum induce very little antirachitic 

 action in lettuce, alfalfa, spinach, New Zealand spinach, and soybean plants, 

 but rays from mercury vapor lamps passing through proper filters supply 

 these plants with appreciable calcifying properties. Neither source of 

 ultraviolet develops antirachitic substance in cabbage. Plants severed 

 from the roots develop vitamin D under ultraviolet exposure much faster 

 than intact plants. The irradiated plants in absence of an effective ultra- 



