792 Wisconsin Academy of Sciences, Arts r and Letters. 
Taking into consideration only those compounds that have 
been isolated, (hydrothymoquinone, thymoquinone, and dihy¬ 
droxy thy moquinone ) or whose presence has been indicated 
(monohydroxythymoquinone) in the Monardas thus far, the 
number of possible pigments becomes truly bewildering. A 
consideration of these possibilities of easily decomposable phe.no- 
quinones and quinhydrones readily explains why a crystalline 
pigment, seemingly a chemical unit, upon recrystallization from 
such a solvent as ether yields several kinds of crystals of dif¬ 
ferent shades of red and purple. To attempt the isolation of 
a number of these pigments would seem a thankless task. In¬ 
deed, after they had been isolated the question might pertinently 
be asked whether the combination as isolated existed as such 
in the plant or whether it had been formed because of a change 
of solvents. 
However, the subject of the pigmentation of the Monardas 
is not solved even after the numerous combinations of pheno- 
quinones and quinhydrones have been worked out. Most of 
these pigments are phenolic in character and hence can com¬ 
bine with metallic constituents, ammonia and organic nitro¬ 
gen bases of the plants giving rise to different shades of the 
original pigment. 
This is shown by the varying shades of color produced by 
treating solutions of these phenols with solutions of basic me¬ 
tallic compounds, etc. However, nothing definite is known of 
the particular kind of metallic and other derivatives which may 
be found in the various parts of the several Monarda species. 
Another possible influence of basic inorganic material re¬ 
mains to be referred to, viz: the stimulating influence some of 
them, such as potassium hydroxide and calcium hydroxide, exert 
on oxidizing reactions, e. g. the oxidation of thymoquinone. 
That even very dilute basic solutions exert such an influence 
has been shown by the action of lime water upon aqueous thy- 
moquinhydrone solution. It has further been demonstrated 
• by Sehaer 10 and others that traces of basic substances, organic 
as well as inorganic, stimulate the action of oxidases. 
Assuming that much of the pigmentation of plants contain¬ 
ing quinones or hydroquinones is due to the formation of 
quinhydrones or phenoquinones, the intense coloration of the 
10 From a reprint from the Pharm. Inst. Strassburg, 1902. 
