786 Wisconsin Academy of Sciences, Arts, and Letters. 
play in the formation of the pigments, can best be illustrated by 
a series of graphical formulas given on the accompanying chart. 
From this chart it becomes apparent that here we have to 
deal with white (or colorless), yellow, orange, and red sub¬ 
stances, all of which are very closely related to each other. More¬ 
over, the thymoquinone, monohydroxythymoquinone and dihy¬ 
droxy thymoquinone, have the capacity of adding monatomic 
phenols, thus yielding highly colored phenoquinones; also diat¬ 
omic phenols thus yielding the equally highly colored quinhy- 
drones. 
Thymoquinhydrone has actually been isolated from the corol¬ 
las of Monarda fistulosa while the formation of phenoquinones 
and quinhydrones of mono- and dihydroxythvmoquinone has 
been considered as a probable explanation of the complexity of 
the mixture of crystalline pigment originally referred to as 
“alizarin-like 9 ).” The following table illustrates the pheno- 
quinone and quinhydrone pigments that can result from the 
addition of the phenols to the quinones thus far observed in the 
Monardas. 
9 Fh. Rev., 19, p. 244 ; Mid. Drug., Ph. Rev., 44, p. 342 ; Bulletin of the 
Univ. of Wis., No. 448, p. 22. 
