80 Dr Gardner on the Action of Light on Vegetables. 



darknessi The greater altitude of the plants in the indigo 

 and violet rays, a fact discovered by Morren, is due probably 

 to the slowness of exhalation by vegetables in those colours, 

 an effect not of light, but of heat. In this observation, no re- 

 sult whatsoever was produced on the original yellow colour of 

 the seedlings in the indigo and violet rays. 



(10). The ensuing table contains the comparable points of 

 six similar experiments. The 1st column gives the number of 

 the observation ; the 2d, the plants used ; the 3d, the number 

 of hours of sunshine ; the 4th, the whole duration of the ex- 

 periment ; and from the 5th to the 1 3th column, the rays of 

 the spectrum ; the figures in the last spaces indicate only the 

 order of colour in the particular observation. The sign of 

 minus is introduced whenever the effect of the ray was not 

 tested, or the result was defective. 



Table, shewing the Active and Inactive liays of the Spectrum, 

 in producing the Green Colour of Plants. 



In experiment 5, the blue ray produced a green colour, but 

 the usual effect was a light olive. The indigo, violet, and 

 lavender portions were always inactive, although several ob- 

 servations were continued until the plants faded. 



(11.) Under favourable circumstances it requires a long ex- 

 posure to develope chlorophyl. The shortest period I wit- 

 nessed was in a crop of turnip seedlings, which required two 

 hours in the centre of the yellow rays, but frequently six or 

 more hours were necessary. In the full sunshine of Virginia, 

 it requires more than one hour to produce the same effect. 



The colour acquired is not fugitive. It has been observed 



