oil of _L. vera_, obtained from Dr. S. Piesse, indicated a specific
gravity of 0.8903 at 15° C., and that its power of rotating the plane of
polarization (observed with a tube ten inches long) was -20°. Compared
with these results he found the sp. gr. of oil of turpentine to be
0.8727, and the rotatory power -79°.

Although _L. stæchas_ was well known to the ancients, no allusion
unquestionably referring to _L. vera_ has been found in the writings of
classical authors, the earliest mention of this latter plant being in
the twelfth century, by the Abbess Hildegard, who lived near
Bergen-on-the-Rhine. Under the name of _Llafant_ or _Llafantly_, it was
known to the Welsh physicians as a medicinal plant in the thirteenth
century. The best variety of _L. vera_--and there are several, although
unnamed--improved by cultivation in England, presents the appearance of
an evergreen undershrub of about two feet in height, with grayish green
linear leaves, rolled under at the edges, when young; the branches are
erect and give a bushy appearance to the plant; the flowers are borne on
a terminal spike, at the summit of along naked stalk, the spike being
composed of six to ten verticillasters, more widely separated toward the
base of the spike; in young plants two or four sub-spikes will branch
alternately in pairs from the main stalk; this indicates great vigor in
the plant, and occurs rarely after the second year of the plant's
growth. The floral leaves are rhomboidal, acuminate, and membraneous,
the upper ones being shorter than the calyces, bracteas obovate; the
calyces are bluish, nearly cylindrical, contracted toward the mouth, and
ribbed with many veins. The corolla is of a pale bluish violet, of a
deeper tint on the inner surface than the outer, tubular, two-lipped,
the upper lip with two and the lower with three lobes. Both the corolla
and calyx are covered with stellate hairs, among which are embedded
shining oil glands, to which the fragrance of the plant is due. The _L.