PENNYROYAL, in botany, a herb formerly much used in
medicine, the name being a corruption of the old herbalist's
name "Pulioll-royall," Pulegium regium. It is a member
of the mint genus, and has been known to botanists since the
time of Linnaeus as Mentha pulegium. It is a perennial herb
with a slender branched stem, square in section, up to a foot
in length and rooting at the lower nodes, small opposite stalked
oval leaves about half-inch long, and dense clusters of small
reddish-purple flowers in the leaf axils, forming almost globular
whorls. It grows in damp gravelly places, especially near pools, on heaths and commons. It has a strong smell somewhat like that of spearmint, due to a volatile oil which is readily obtained by distillation with water, and is known in pharmacy as Oleum puleggi. The specific name recalls its supposed property of driving away fleas (pulices). Like the other mints it has carminative and stimulant properties.