274 Influence of Light. 



ted in the leaves, and the deeper shades which plants acquire 

 in the autumn and summer, when they have accumulated a 

 greater stock. The variety of colors at the fall of the leaf 

 which is presented to us, Macaire supposed was owing to the 

 absorption of oxygen, which thus produced various colored 

 rusts, and to which also the different colors of flowers he 

 thinks may be likewise attributed. Humboldt met with some 

 green plants growing in complete darkness, at the bottom of 

 one of the mines of Freuberg, which he attributed to the pre- 

 sence of hydrogen, which abounded in the mine. Another 

 effect of the intensity of light is to make plants remarkably 

 hard and firm in their texture, owing to the vigor they receive 

 from its influence, but it also makes them of smaller dimen- 

 sions. In hot climates, both causes, heat and light, operate 

 and produce the remarkable results we have often noticed with 

 wonder. Plants deprived of these genial influences are 

 strangely altered in every respect. The celebrated Dr. Robin- 

 son, of Edinburgh, gives an account of a plant found in the 

 drain of a coal work under ground, which was very luxuriant, 

 with large indented foliage and perfectly white. He had never 

 seen anything like it, nor could any one inform him what it 

 was. He had the plant with a sod brought to the open air in 

 the light, when in a little time the leaves withered, and soon 

 after new leaves began to spring up of a green color, and dif- 

 ferent shape from the old ones. On rolling one of them be- 

 tween his fingers he found that it had the smell of common 

 tansy, and it ultimately proved to be that plant, which had 

 been so changed by growing in the dark ; indeed it was re- 

 collected that some soil had been taken into a drain from a 

 neighboring garden, some time before it was found so altered. 

 The Abbe Tassier ascertained by experiment, that the green 

 color of vegetables may be produced by artificial light in the 

 absence of the sun. Kept in the dark, plants become dropsi- 

 cal, and have both smell and flavor diminished ; advantage 

 has been taken of this circumstance to soften the smell of vege- 

 tables when too strong. That of celery is tempered by bury- 

 ing the stem in the ground and sheltering it from the light, 

 while the leaves alone are suffered to appear above ; these last 

 have of course the usual green color and fulfil their necessary 



