46 Miss M. Wheldale. Colours and Pigments of [Oct. 31, 



from chlorophyll ; in unpigmented genera, Galanthus nivalis, for instance, 

 or in pigmented (anthocyanic) genera such as many Umbelliferce, with white 

 flowers, the petals turn bright canary yellow with ammonia. 



The inheritance of colour in Antirrhinum (Wheldale (12) ) has led to the 

 suggestion that anthocyanin is possibly a compound of such a glucoside-like 

 body with a reddening substance. The original type of Antirrhinum has 

 magenta (anthocyanin) flowers.* Loss of the reddening substance, which 

 may be represented by a Mendelian factor (M), gives a variety bearing 

 ivory-white flowers containing no pigment (except in the palate and hairs), 

 but a glucoside-like body giving the reactions with acids, alkalis, and lead 

 acetate described above. Further loss of a substance, again represented by 

 a factor (I), from the glucoside-like body in the superficial cells of the lips 

 gives a yellow xantheic pigment, and the variety thus bears yellow flowers. 

 Loss of yellow pigment, represented by yet another factor (Y), gives an 

 .albino, containing no pigment and no glucoside-like body. Local decom- 

 position produces the same xantheic pigment on the palate and in hairs on 

 the inner surface of the tube in all vatieties except the albino. The albino 

 may carry I or M, or both, since these factors are invisible unless the 

 fundamental colour Y is present. Moreover, the reddening factor can exist 

 with Y, the decomposition product, giving a mixed colour, i.e., crimson. 

 Each variety may breed true or may throw itself and one or more varieties 

 below it in the scale of colour, according as it is homo- or heterozygous in 

 the various factors. Magenta can throw all varieties ; crimson can throw 

 yellow and white ; ivory, yellow and white ; and yellow, white only. 



At this point it is interesting, perhaps, to give views regarding the consti- 

 tution of anthocyanin, based on results obtained from a totally different 

 kind of investigation. Overton (9) found that in plants supplied artificially 

 with excess of sugar and other carbohydrates there is a correlated increase in 

 the production of anthocyanin, and he concludes that the latter, in many 

 cases, is a glucoside compound of a tannic acid. Molisch (8) and Heise (6) 

 are also of the opinion that some red sap-pigments are glucosidal in nature. 

 Tannin is by no means always present in plants containing anthocyanin ; the 

 magenta pigment of Antirrhinum gives a tannin reaction, but no tannin has 

 been found in the albinos. 



A similar range of colour to that found in Antirrhinum, i.e., various shades 

 of purple or magenta and crimson, together with ivory, yellow, and sometimes 

 white, also occurs in Althaea rosea, Azalea, Dahlia variabilis, Dianthus 

 'Caryophyllus, Helichrysum bracteatum, Linaria, Nemesia, Phlox Drummondii, 



* With yellow pigment locally on the palate and in hairs on the inner surface of the 

 ■tube. 



