PHYSICAL AND METEOROLOGICAL RESEARCHES. 113 



flowers are to the same effect. It has been known for some time that 

 to obtain white lilacs it is only necessary to place colored lilacs, espe- 

 cially the Marly variety, in a hothouse kept at a constant temperature 

 of 15° C. Duchartre states that the lilac would become white if placed 

 in a very light hothouse if the temperature remained constantly at 

 15° C. He attributes the decoloration of the flowers to the more ener- 

 getic oxidation of the air of the hothouse. 



The experiments of the author were conducted on Marly and Persian 

 lilacs, planted in colored hothouses andin theopen air. The panicles were 

 budded and at the time of planting were slightly colored. In the white 

 hothouse the lilacs became pink and almost entirely lost their color. 

 In the red, green, and bine houses they become absolutely white. The 

 hothouses had a varying temperature, during the night falling to 1° 

 and rising during the day to 2o°. Lilac buds inclosed in a dark hood 

 become discolored notwithstanding the temperature was the suine as 

 in the surrounding air. If the panicles were inclosed when already 

 more or less colored red shades were obtained. Thus it is possible to 

 obtain on one stem flowers of all shades between the white and violet 

 red. If panicles already colored are placed under a colored bell jar, flow- 

 ers varying from pale blue to clear red violet will be obtained. These 

 results are neither due to temperature nor to activity of growth, but are 

 evidently caused by differences in light. 



The writer's experiments covered a great number of plants, and it 

 was found possible to change the form, size, and color of the leaves 

 of plants with different colored light. Among the most remarkable 

 results were those obtained with the Coleus. In the accompanying 

 plate some of the differences observed on this plant due to its culture, 

 character of solar rays, or the different intensity of light are shown. 



In Plate I, A represents a leaf exposed to full radiation in the white 

 hothouse, and B one grown in the red hothouse. It can be seen that 

 the red pigment decreased in red light, the leaf spread, and its form 

 changed. Leaf C, grown under the green-colored glass, is diminished 

 in size, the red pigment has disappeared, being replaced by a yellow 

 coloration. In leaf I), grown in blue rays, the red pigment has almost 

 completely disappeared. On the same plate are also shown four other 

 leaves of Coleus, the first grown in the open air, the second under a 

 slightly diffused light through a garden frame, the third in diffused 

 light, and the fourth under a still weaker light. The transformation 

 of the plant in this case is gradually accomplished under an attenua- 

 tion of light, as in the preceding case under the influence of different 

 rays. The largest and most curious leaf is the third. The fourth was 

 greatly diminished and modified, having changed from poppy red with 

 a dark edge to yellow and light green. 



Comparing these eight Coleus leaves it will be seen that the leaf from 

 the hothouse under total radiation has developed much more than the 

 one grown in the open air; that those from the red house and diffused 



