ANTHOCYANINS 337 



and is generally ascribed to the presence of the pigment 

 anthocyanin. It is, however, doubtful whether all such 

 colorations are due to anthocyanins ; thus Molisch found that 

 the red colour assumed by the leaves of the aloe, on exposure 

 to high insolation, is due to the formation of carotin within 

 the chloroplasts. 



The presence of anthocyanin is due to many causes,* light, 

 especially when of high intensity, being important. For ex- 

 ample, apples and other fruits and also the vegetative organs 

 of certain plants will not assume a red colour if kept in 

 darkness. Jonesco f observed that buckwheat seedlings when 

 placed in the dark lost their red colour, the total amount of 

 fiavone and anthocyan glucosides falling to about one-sixth 

 after ten days' darkening. On the other hand, light does not 

 appear to be of such importance in the case of the roots of the 

 beet. 



In other instances the aerial vegetative organs of many 

 varieties of plants, e.g. certain Chenopodiaceae, are charac- 

 terized by a red colour, the presence of which is seemingly 

 independent, or nearly so, of external conditions. Thus 

 Salicornia ramosissima may be found in two forms, one apple 

 green and the other crimson, the intensity of which varies in 

 different years. In such cases there is good reason for sup- 

 posing that these colours are of an hereditary nature and 

 come true from seed. The same also appears to be true for 

 different forms of beet which are used for horticultural pur- 

 poses. On the other hand, in the familiar example of the 

 copper beech this is not so, the copper-coloured foliage, due 

 to the combined effect of a red cell sap and the green of the 

 chlorophyll, first originated, it is stated, as a sport and is 

 propagated by means of cuttings. 



According to Pick and others, anthocyanin is commonly 

 associated with tannins, for a red sap is characteristic of 

 tannin-containing plants, and the precipitate appearing in the 

 palisade cells of Hydrocharis on treatment with caffeine and 



* See also Wheldale-Onslow : " The Anthocyanin Pigments of Plants," 

 Cambridge, 1925. 



t Jonesco : " Compt. rend.," 1921, 172, 1311. 



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