4 Dr. Gardner on the Action of Light upon Vegetables. 



result indicated was obtained by a comparison of the whole. 

 The age of seedlings is a matter of moment ; those which are 

 young, and from one inch to one inch and three fourths high, in 

 the case of turnips, were most sensitive ; indeed, these plants 

 were found to give the best results, and were used almost exclu- 

 sively after the first month. 



The spectrum was allowed to fall on the specimens at a dis- 

 tance of fifteen feet from the prism, and undecomposed light shut 

 out by screens. Each ray acted in a separate compartment, un- 

 less otherwise stated. 



(9.) The following extract of an experiment, will show some 

 farther details. 



August 13th. — Five jars, containing each about one hundred 

 turnip seedlings, were placed respectively in the orange, yellow, 

 blue, indigo, and violet rays at 9h. A. M. Day, bright — tempe- 

 rature in shade at noon 80° Fah., in the sun 95°. Duration of 

 sunshine 6£ hours. Result at 3=|h. P. M. The third column of 

 the table shows the altitude of the plants at the commencement 

 of the observation. 



August lAth. — The same plants with the addition of a fresh 

 crop (6) in the green ray. Exposure from 9h. A. M. to 3h. P. M. 

 or six hours sunshine. Temperature in shade at noon 85° Fahr., 

 and 105° in the sun. Result at 3h. P. M. 



* The fifth column contains a comparative estimate of the depth of color, as- 

 suming unity at the highest value; on this scale the plant in blue light did not 

 become green, and the value is negative, but there was a visible alteration desig- 

 nated olive, and indicating the tint which vegetables assume in passing from the 

 vellow color of darkness to green. 



