78 Dr Gardner on the Action of Light on Vegetables, 



my results and those of Mr Hunt, for I do not esteem re- 

 searches such as all the foregoing, made with coloured media, 

 of any value in this branch of vegetable physiology. It is well 

 to remark, however, that in treating of the germination of 

 cress seed behind the blue, green, yellow, and red media, he 

 states, " that the earth continued damp under the green and 

 blue fluids^ whereas it rapidly dried under the yellow and red^ 

 (p. 271). This difference would by most persons have been 

 considered sufficient to retard or " destroy" \ germination. 



(6.) Other engagements in 1842 interfered with my design 

 of examining this question with the spectrum ; and it was not 

 until July 1843, that such arrangements were made as are ne- 

 cessary to the prosecution of the subject. 



(7.) The apparatus. A beam of the sun's light was direct- 

 ed by a heliostat placed outside my window, along a square 

 tube of wood, passing through the shutter. The inner extre- 

 mity of the tube was closed, and contained near its end a flint 

 glass equilateral prism, one inch on the side and six inches 

 long, with the axis adjusted perpendicularly. The dispersed 

 light passed into the chamber through an aperture in the side 

 of the tube. All that portion of the beam which exceeded 

 the breadth of the prism was cut off by a diaphragm. The 

 object of these arrangements was to render the room dark. 

 The experiments were performed in Virginia, in lat. 37° 10' 

 N., and continued from July 6 to October 1, during a season 

 of unusual brilliancy and temperature. 



(8.) Arrangements for the experiments. Seedlings of tmv 

 nips, radish, mustard, pease, several varieties of beans, peas, and 

 the following transplanted specimens, were used, Solanum ni- 

 grum, S. Virginianum ; Plantago major, P. minor ; Polygonum 

 hydropiper ; Chenopodium rubrum ; Bumex obtusifolius. They 

 were placed in boxes with partitions, or planted in jars, and 

 grew in darkness until ready for experiment, so that they ac- 

 quired a yellow colour. The number of plants exposed to 

 each ray averaged one hundred, when the smaller seeds were 

 used, and the 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 ono inch to one inch and 



