32 LIGHT. 



(c.) Their pungency and aromatic properties depend very much 

 upon the light. 



-Plants growing in the dark "contain an excess of saccharine and 

 aqueous particles 5" they are destitute of color, odor, and pungency, 

 but acquire these properties if transferred to the light.* 



(d.) Light is most abundant in the torrid zone, and there the ver- 

 dure is the most intense ; there also we find the richest gums and 

 resins and the most odorant aromatics, and the foliage is there most 

 abundant ; but other causes besides light contribute to these effects, as 

 heat and moisture. 



(e.) Light extricates oxygen gas from fresh green vegetables, 

 which may be collected in an inverted bell glass, full of water, and 

 containing the plant also. Carbonic acid gas is evolved in the night. 



(/.) Light is a stimulus to vegetables. Their leaves incline to- 

 wards the light : plants growing in windows do this : some flowers 

 open their petals to the light and shut them at night. 



Camphor kept in glass bottles exposed to light, crystallizes in the 

 most beautiful symmetrical manner, and more particularly on the side 

 next to the light. 



(g.) Light sometimes weakens or discharges color. Yellow wax 

 in thin layers becomes white ; stamped goods, as curtains, and those 

 stuffs that are colored in the thread, as carpets, have their colors 

 faded by light : these colors are usually of vegetable origin, modified 

 more or less by mineral mordants. 



16. LIGHT ACTS ON ANIMALS. 



(a.) Light exalts the color of animals. Worms, grubs, and larger 

 animals that live in the ground, are generally possessed of dull colors, 

 without beauty or vivacity. 



Birds and insects of night are generally of dull hues. Owls, 

 night-hawks, whip-poor-wills, certain varieties of snipes or wood- 

 cocks, &c. and the insects of summer evenings, have generally no 

 beauty of color. 



(b.) The opposite is true of a great proportion of the various 

 classes of animals that are much abroad in the day light. 



Generally the vivacity of color is greatest in the animals, birds and 

 insects of the tropical regions, and the opposite is true of die polar : 

 the temperate, as we might suppose, occupy a middle rank in these 

 respects. 



* Dr. Robinson, " in the drain of a coal work under ground, accidentally laid his 

 hand upon a very luxuriant plant, with large indented foliage and perfectly white. 

 He had not seen any thing like it, nor could any one inform him what it was. 

 He had the plant with a sod, brought into the open air in the light. In a little 

 time the leaves withered and soon after new leaves began to spring up of a green 

 color and of a different shape from that of the old ones. On rubbing one of the 

 leaves between his fingers, he found that it had the smell of common tansy, and 

 ultimately proved to be that plant, which had been so changed by growing in the 

 dark." Rees' Cyclopedia. 



