114 Chemistry of Memlelian Factors Jor Floiver-Colonr 



was thereb}' purified from oxidised products formed in hydrolysis. The 

 ether extract was crystallised from alcohol, the crystals being in the 

 form of pale yellow plates. The pigment was next converted into its 

 acetyl derivative by boiling with acetic anhydride. The acetyl deriva- 

 tive is pure white (owing to replacement of the hydroxyl groups by the 

 acetyl residue) and crystallises in long needles. The pigment may be 

 again obtained in a completely pure state by hydrolysing the acetyl 

 derivative with alcoholic soda solution. From the analyses and melting 

 points of the acetyl derivative and of the pure pigment (Wheldale and 

 Bassett, 33), the latter was identified with apigenin, a fiavone of known 

 constitution occurring in Parsley (Apium Petroselinum), and in small 

 quantities in Reseda luteula : 



O 



HO 



OH 



HO CO 



The yellow pigment of the yellow variety was found to be present 

 in the epidermis only of the lips of the corolla, the inner tissues con- 

 taining apigenin. Hence the crude pigment, prepared in the way 

 described above from the upper lips of the yellow variety, always 

 consisted of a mixture of apigenin and yellow pigment. From pre- 

 liminary experiments it seemed likely that the yellow pigment was the 

 flavone, luteolin. On this assumption, a separation of the two pigments 

 was brought about by means of hydrobromic acid which forms a com- 

 pound with luteolin but not with apigenin. The yellow pigment was 

 identified with luteolin by means of its melting point and other 

 properties and the melting point' of its benzol sulphonyl derivative 

 (Wheldale and Bassett, 34). Luteolin has been isolated from Reseda 

 luteolu and it is also found in Genista tinctoria and in leaves of Digitalis. 

 It is represented as : 



P ,OH 



HO 



OH 



CH 



HO CO 

 and owes its intense colour to the ortho-position of the two hydroxyl 

 groups in the side ring, which structui-e does not occur in apigemn. 



