COLOR. 143 



This tlicory has boon attacked by the most al)lo physiolo- 



is, and thev have consiilered theinsolvcs siiccisst'id in |)()int- 

 out errors in exj)eriinei)ts and observations which are 



i'lcient to invahdate lliis extensively received theory. INIohls, 

 in a memoir in the Annalrs des Sciences JMaturc lit x, Vol. ix. 

 p. 21*2, exannnes various thef)ri':s on this subject, witli appa- 

 -' nt imparlialily, and <j;ives his decided preference to the fol- 



A ing theory t)tAIac(iiKirt, altliougli it does not receive his 

 unqualiticd approbation. 



203. Macquart aibnits tliat »be various colors are owing to 

 •^-i^ various luoditieations ol Chlorophyll, but denies that it is 



ing to its being o\ydiz"d by acids, ordisoxyd.zed by alkalis. 

 But that it is converted into two distinct substances, by the 

 aduition and abstraction of water. By the loss of water it is 

 converted into a blue substance, called anthocyanc^ which is 

 soluble in water, but not in alcohol. By the addition of wa- 

 ter, the chlorophyll is converted into a yellow substance, called 

 anthoianth'uiPy wliich is partly soluble in alcohol, and partly 

 in water. Tluse two substances form the basis of the two 

 series of colors above given. They both sometimes exist in 

 the same llower, but occupy difTjrent cells; the anlhoxantiiine 

 being situated in the inferior cells, while the anthocyane oc- 

 cupies the superficial ones ; this gives a great variety of tints, 

 according as the ccdor of the inferior cells are more or less 

 distinctly exhibited through the superior layers. By the ac- 

 tion of acid and alkaline secretions, these substances assume 

 every variety of hue ascribed to the action of the same agents 

 on chromule. 



204. The outward circumstances, wbicli tend to change the 

 color of vegelahle organs, are various. The action of light 

 is one of tiie most efficient agents in the production and change 

 of colors; and it is not a little singular, that the power, which 

 is absolutely necessary to the production of color, in the great 

 majority of cases, should be the most powerful agent in de- 

 stroying it. We are all acquainted with the influence of 

 '■"ht in hi inching vegetable substances when dead. The 



mge of the color of leaves in autumn, of fruit when ripen- 

 ing, of some ever green leaves during the winter, are phenom- 

 ena whose explanation, has as yet baffled the most acute ob- 

 servers. The memoir of Mold, al)ove quoted, leads us one 

 step farther than had Ixifore been taken in the explanation of 

 these common phenomena. 



205. We can only give in few words, the results to which 

 his extended observations have led him. He concludes that 

 these various changes are owing to a derangement or suspen- 



