polarization (observed with a tube ten inches long) was -20 deg.. Compared
with these results he found the sp. gr. of oil of turpentine to be
0.8727, and the rotatory power -79 deg..
Although _L. staechas_ 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.
vera_ was identified in 1541, and introduced into England in 1568,
flourishing remarkably well under cultivation, and yielding an oil far
superior in delicacy of fragrance to that obtained from the wild plant,
or to that obtained from the same plant cultivated in any other country.
When it is remembered that north of the 50th degree of latitude the vine
yields little but garlands of leaves, and that we should attempt in vain
to cultivate the olive north of the 44th degree, it may seem strange
that the _Lavandula vera_, which is a native of about the same climate
as these, should resist, unprotected, the vigorous frosts of this
country. Even at Upsala, latitude 59 deg. 51' N., in the Botanic Garden, it
merely requires the shelter of a few branches to protect it in the
winter; but this hardiness may be accounted for by several physiological
reasons. Like all fruticulose labiates which have a hard compact tissue
and contain much oily matter, the lavender absorbs less moisture than
herbs which are soft and spongy, and, as it always prefers a dry
calcareous, even stony, soil, the northern cultivators find that by
selecting such localities the tissues of the plant take up so little
water that the frost does not injure them.
In a northern climate the length of the days in summer, and the natural
dryness of the air, compensate in some measure the reduction of
temperature, and mature the plant only to the extent sufficient for the
purpose for which it is grown. Perhaps the suspension of vital action
during winter, which must be more complete in northern latitudes, as our
frosts are more severe, tends to preserve certain plants, native of the
south, for it is observed that all plants are more sensitive to cold
when vegetation is active than when it is at rest. The vine is an
instance of this. On the other hand, when the plant is cultivated
further south than its natural boundary, the same causes seem to exert
their influence, but in the reverse sense. Lavender is cultivated on the
mountains of Yemen, in Arabia; the humidity, increasing inversely to the
latitude, compensates the exhaling force of the sun's rays, and the
elevation of the locality the effects of the heat.
Thus is confirmed, both in north and south, the law of vegetable
physiology observed by De Candolle, in the temperate climates of France,