112 



EXPERIMENT STATION RECORD. 



more definite results. The maize plants were fifteen days old; the 

 stems were equally vigorous, and each bore five leaves. The experi- 

 ment was begun September 14, with an average temperature of 20° C, 

 and each leaf was inclosed in a glass tube. The experiment lasted 26 

 hours, and the transpired water was as follows: 



Effect of different colors on transpiration of maize. 



Color. 



Weight 

 of leaf. 



transpired per » 



of leaf. 



Red 



Yellow 



Green with some yellow rays 

 Violet 



It will be seen that the maximum transpiration occurred in the 

 orange-yellow and the minimum in the violet portion of the spectrum. 



ACTION OF DIFFERENT PORTIONS OF THE SPECTRUM ON THE COLOR 

 OF VEGETABLE TISSUES. 



The many different colors of plants are mostly due to light. The 

 green color of the leaves, due to chlorophyll, can only be produced in 

 the light. The blue, yellow, red, and other colors are partly due to 

 pigments and partly to cell sap. The writer has investigated the role 

 of light in the coloration of the different tissues of flowers, fruits, etc. 



For these researches colored-glass hothouses and absolutely mono- 

 chromatic solutions were used. The solutions were contained between 

 the walls of special vessels in the interior of which the flowers, fruits, 

 leaves, etc., were exposed. The red was obtained from a solution of 

 carmin in ammonia, the green from a concentrated solution of copper 

 chlorid, and the blue from a solution of copper sulphate and ammonia. 

 According to Sachs, the development of the coloring matter is inde- 

 pendent of the action of light. It is developed in the leaves at the 

 expense of substances which are produced under the action of light. 

 The author's experiments indicate that light acts not only on the nutri- 

 tion of the plant, but also on the coloring of the tissues. It sometimes 

 exerts a direct action on the flower, and in this case the coloring is due 

 principally to light. 



Plants may be classified according to the cause of coloration into 

 three groups, namely, those in which coloration is due (1) to the direct 

 action of light, (2) to the action of the light and to the food material 

 in the leaves, and (3) to other causes than the action of light. Chloro- 

 phyll is directly due to the action of light. It is not immediately de- 

 stroyed when the plant is placed in darkness, but remains unchanged 

 as long as the plant has not exhausted its reserve, disappearing only 

 when the reserve material has been exhausted. Observations on 



