242 THE CHEMISTBY OF ESSENTIAL OILS
Sample No. 1 was examined by Brandel,
1
the remainder by Schim-
mel & Co.
2
Neither thymol nor carvacrol are present in the oil.
Monarda fistulosa.—This plant is known in North America as the
wild bergamot. The fresh herb yields from O3 to 1 per cent, of essen-
tial oil, and the dried herb, about 2-7 per cent.
The oil has a specific gravity varying from 0
- 915 to 0'959, according
to the part of the plant distilled, and is slightly laevo-rotatory. Its
phenol-content is about 50 to 70 per cent.
The oil has been exhaustively examined by E. B. Miller,
3
who finds
the following substances present therein: 5-a-pinene, Z-a-pinene, p-
cymene, one or two unidentified terpenes, butyric aldehyde, iso-valeric
aldehyde, a third aldehyde, possibly piperonal, carvacrol, thymoquinone,
hydro-thymoquinone, dihydroxy-thymoquinone, dihydrocuminic alcohol,
an unidentified alcohol, acetic acid, butyric acid, valeric acid, caproic
acid, basic substances, and (in the aqueous distillate) acetone, form-
aldehyde, methyl alcohol, formic acid, and acetic acid.
OIL OF PENNYROYAL.The leaves and other parts of the plant Mentha pulegium yield the
ordinary pennyroyal oil. This plant is a native of most parts of Europe,
the Caucasus, Chili, Teneriffe, etc. The volatile oil is of a yellow or
greenish-yellow colour, and possesses a strong odour of the plant.
E. M. Holmes* gives the following account of this herb :—
" Two forms of the plant are met with in this country, the commonest
form having weak, prostrate stems, which root at the joints and form a
dense green turf. This is named var. decumbens. The flowering stems
are sparingly produced, and often lie prostrate on the leafy cushions of
the plant.
"The other form, known as var. erecta, has stouter upright flowering
stems, which end off lateral stolons or prostrate branches near the
base. These root sparingly, forming new plants, which gives rise to
upright flowering stems during the ensuing year. This is much rarer
as a wild plant, but is the best for cultivation, as it can be reaped
and tied up into bundles more readily. The stems are usually 6 to 9
ins. long, but under favourable conditions, such as moist soil and a
warm climate like that of Devon and Cornwall, will grow to 15 or 18
ins. There are several other varieties of this plant found on the Con-
tinent. One variety, eriantha, with hairy flowers, occurs at Biarritz,
and a similar form has been found near Falmouth, in this country.
Another, in which the whole plant is hairy, is found in Sicily, and is
named var. tomentosa, and a third, covered with rather stiff hairs, named
var. tomentella, is found near Montpelier and in Hungary. A fourth,
with small leaves, occurring in Eastern Europe is named var. thymifolia,
and on the steppes of Southern Russia a hairless variety with smaller
leaves and flowers, has been described as a variety, but as it is an an-
nual plant it has probably the right to specific raak, and should be
called Mentha micrantha. It has been called Pulegium micranthum.
"Of these varieties it is uncertain which are used on the Continent
as sources of the oil, but the plant used in Spain, so far as can be judged
2 lPharm. Rev., 21 (1903), 109.
Bericht, October, 1904, 101; October, 1908, 89 ; October, 1909, 78.
•> Circular 4 (1918), University of Wisconsin.^4 P. and E.O.R. (1911), 254.