1^0 COLOR. 



varieties of color are owing, produced by the accession of these 

 different substances, as it is well-known that almost every hue 

 may be produced by these two metals. But the quantity of 

 chromule which exists in plants is exceedingly small ; Berzelius 

 estimated the quantity in the leaves of a large tree not to exceed 

 three and a half ounces. 



242. To enable plants to deposite chromule, light, in most 

 cases, is absolutely necessary. This is abundantly shown by the 

 fact, that plants growing in the dark become blanched ; not that 

 the chromule already deposited becomes less, but that it is sur- 

 rounded by the deposition of substances containing no chromule, 

 and of course becomes less observable. There are examples, 

 however, of plants growing in deep mines, having never enjoyed 

 the light of day, which, nevertheless, are green. 



243. Green is considered the natural color of vegetation, and 

 when it is not of this hue, in the language of Botany, it is said 

 to be colored. 



244. The change of color produced on chromule has been 

 referred to different causes. The two most deserving of notice 

 are the one of Schubler and Funck of Tubingen, and the other 

 of Macquart. 



Both theories consider green as the original color, but the 

 means by which the variations are produced are accounted for 

 on very different principles by the supporters of the two theories. 

 Schubler and Funck maintain that all variations from green are 

 produced by acid or alkaline secretions. The green chromule, 

 acted on by these substances, assumes every variety of hue. 

 The hues assumed by the flowers are determined by the different 

 agents by which they are produced, with the exception of red ; 

 this is common to both. Those produced by the action of the 

 alkaline secretions, from green, are — 



Greenish-blue, Violet-blue, Violet-red, 



Blue, Violet, Red. 



This is called the Blue, Cyanic^ or Deoxydized series, and any 

 variation of color from one of these hues will always be by 

 passing into some other of the same series. 



Those colors produced by the acid secretions are — 



Yellow-green, Orange-yellow, Orange-red, 



Yellow, Orange, Red. 



242. "What agent is necessary for the production of chromule? Yiovt 

 shown? — 243. The natural color of vegetation? — 244. The theory of Schu- 

 bler and Funck ? Give the blue Bcries. The vellow. 



