Leaf (lēf), n.; pl.
Leaves (lēvz). [OE. leef, lef,
leaf, AS. leÁf; akin to S. lōf,
OFries. laf, D. loof foliage, G. laub, OHG.
loub leaf, foliage, Icel. lauf, Sw. löf,
Dan. löv, Goth. laufs; cf. Lith. lapas.
Cf. Lodge.] 1. (Bot.) A colored,
usually green, expansion growing from the side of a stem or
rootstock, in which the sap for the use of the plant is elaborated
under the influence of light; one of the parts of a plant which
collectively constitute its foliage.
☞ Such leaves usually consist of a blade, or lamina ,
supported upon a leafstalk or petiole, which, continued
through the blade as the midrib, gives off woody ribs
and veins that support the cellular texture. The petiole has
usually some sort of an appendage on each side of its base, which is
called the stipule. The green parenchyma of the leaf is
covered with a thin epiderm pierced with closable microscopic
openings, known as stomata.
2. (Bot.) A special organ of
vegetation in the form of a lateral outgrowth from the stem, whether
appearing as a part of the foliage, or as a cotyledon, a scale, a
bract, a spine, or a tendril.
☞ In this view every part of a plant, except the root and the
stem, is either a leaf, or is composed of leaves more or less
modified and transformed.
3. Something which is like a leaf in being
wide and thin and having a flat surface, or in being attached to a
larger body by one edge or end; as : (a) A part of a
book or folded sheet containing two pages upon its opposite sides.
(b) A side, division, or part, that slides or is
hinged, as of window shutters, folding doors, etc.
(c) The movable side of a table. (d)
A very thin plate; as, gold leaf. (e) A
portion of fat lying in a separate fold or layer. (f)
One of the teeth of a pinion, especially when small.
Leaf beetle (Zoöl.), any beetle
which feeds upon leaves; esp., any species of the family
Chrysomelidæ, as the potato beetle and helmet
beetle. -- Leaf bridge, a draw-bridge
having a platform or leaf which swings vertically on hinges. --
Leaf bud (Bot.), a bud which develops
into leaves or a leafy branch. -- Leaf
butterfly (Zoöl.), any butterfly which, in
the form and colors of its wings, resembles the leaves of plants upon
which it rests; esp., butterflies of the genus Kallima, found
in Southern Asia and the East Indies. -- Leaf
crumpler (Zoöl.), a small moth (Phycis
indigenella), the larva of which feeds upon leaves of the apple
tree, and forms its nest by crumpling and fastening leaves together
in clusters. -- Leaf cutter
(Zoöl.) , any one of various species of wild bees of
the genus Megachile, which cut rounded pieces from the edges
of leaves, or the petals of flowers, to be used in the construction
of their nests, which are made in holes and crevices, or in a leaf
rolled up for the purpose. Among the common American species are
M. brevis and M. centuncularis. Called also rose-
cutting bee. -- Leaf fat, the fat
which lies in leaves or layers within the body of an animal. --
Leaf flea (Zoöl.), a jumping plant
louse of the family Psyllidæ. -- Leaf
frog (Zoöl.), any tree frog of the genus
Phyllomedusa. -- Leaf
green.(Bot.) See Chlorophyll. --
Leaf hopper (Zoöl.), any small
jumping hemipterous insect of the genus Tettigonia, and allied
genera. They live upon the leaves and twigs of plants. See Live
hopper. -- Leaf insect
(Zoöl.), any one of several genera and species of
orthopterous insects, esp. of the genus Phyllium, in which the
wings, and sometimes the legs, resemble leaves in color and form.
They are common in Southern Asia and the East Indies. --
Leaf lard, lard from leaf fat. See under
Lard. -- Leaf louse
(Zoöl.), an aphid. -- Leaf
metal, metal in thin leaves, as gold, silver, or
tin. -- Leaf miner (Zoöl.),
any one of various small lepidopterous and dipterous insects,
which, in the larval stages, burrow in and eat the parenchyma of
leaves; as, the pear-tree leaf miner (Lithocolletis
geminatella). -- Leaf notcher
(Zoöl.), a pale bluish green beetle (Artipus
Floridanus), which, in Florida, eats the edges of the leaves of
orange trees. -- Leaf roller
(Zoöl.), the larva of any tortricid moth which makes
a nest by rolling up the leaves of plants. See Tortrix. -
- Leaf scar (Bot.), the cicatrix on a
stem whence a leaf has fallen. -- Leaf sewer
(Zoöl.), a tortricid moth, whose caterpillar makes a
nest by rolling up a leaf and fastening the edges together with silk,
as if sewn; esp., Phoxopteris nubeculana, which feeds upon the
apple tree. -- Leaf sight, a hinged sight
on a firearm, which can be raised or folded down. --
Leaf trace (Bot.), one or more
fibrovascular bundles, which may be traced down an endogenous stem
from the base of a leaf. -- Leaf tier
(Zoöl.), a tortricid moth whose larva makes a nest by
fastening the edges of a leaf together with silk; esp., Teras
cinderella, found on the apple tree. -- Leaf
valve, a valve which moves on a hinge. --
Leaf wasp (Zoöl.), a sawfly. -
- To turn over a new leaf, to make a radical
change for the better in one's way of living or doing.
[Colloq.]
They were both determined to turn over a new
leaf.
Richardson.