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Twenty‐seven flavonoids have been identified variously in leaf extracts of the five known chemical races of barley. Five are flavone O‐glycosides, the remainder being C‐glycosylflavones based on apigenin, luteolin or chrysoeriol. Most of the variation is due to the attachment of various sugars, including galactose, to the C‐glucosyl moieties in the 6‐positions, but there are also a range of 7‐O‐glycosides, including two with acyl attachments. Analyses of the results indicate that race A is closest to race C, races B1 and B2 are very similar and race S is about equidistant from A, B1 and C. Genetic evidence shows that the S pattern is the original one and that the others have evolved from it; the chemical results are completely consistent with such an interpretation.

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Dissolve 4.0 ml of cinnamaldehyde in 25 ml of 95% ethanol, add 15 ml of 2 M KOH, and swirl to form a homogeneous solution. Provide acetone, a 1-ml pipet, and a timing device. DEMONSTRATIONWhile stirring, add 1 ml of acetone to the solution of cinnamaldehyde in alcoholic potassium hydroxide.