Evening star., 1924-11-23

w eSrd 90 ins and mapieT lseTless 'eFn noS 10
evergreeuS keep
their leaves In Rock
Creek Park nature is at her best now.
The trees must prepare for Winter just
as people do. But how often do we
realize the trees have been preparing
since Summer?
Leaves are the lungs Of the trees and
through the leaves Transportation goes
on. a process similar TO perspiration III
animals
In the Winter the roots cannot gather
as much moisture as in Summer. accord
ing TO the American Nature Association
of Washington. AS the tree can i'll sf-
ford any great loss through evaporation
in the leaves, il discards them. carrying
on respiration through the bark alone
But the lessening CT moisture in the
soil is not the only factor. We often
feel sorry for the snow-laden branches
OF the graceful birches and for the ever
green boughs weighted down BY load
too great for their strength II the
leaves remained on the naples and ei!ns
about US some snowy morning we would
find the branches torn by the additional
weight of the snow and ice adhering 10
the broad leaves
Trees do not cast away their
leaves thoughtlessly. however, for
stance in each leaf" says Nature
Magazine. In early Autumn this
substance is slowly withdrawn into
the branches and tree proper. A sep
aration layer of tissue at the base OF
the leaf-stalk gradually forms, and
as the time approaches when the leaf
must fall, this tissue becomes more
and more of mucilaginous nature.
The leaf is then held only by the
outer skin and woody strands which
connect the wood of the twig to the
veins of the leaf. Only the frame
work is left and the colors caused by
the disintegration of the green chlo-
rophyll. The leaf is now ready for
some outside agency to step in and
complete the task:
"A warm, sunny day in October
brings with it literal shower of
dancing, swirling leaves. A frosty
morning quickly leaves a tree devoid
of foliage, while during the days be-
tween scarcely a leaf detaches itself.
On warm Fall day the dry air
shrivels the leaf and shrinks the base,
causing it to rupture and fall. The
elms and the birches seem to divest
themselves almost entirely on one
of these days.
Then some morning, when the
frost has blanketed the grass in white
poplars fall steadily to the ground.
Ice crystals had formed in the sticky
separation layer, and, when the
warmth of the sun thawed and eX-
panded them the woody tissue was
torn and the leaf pushed free. Again,
a wet, humit day may dissolve the
tissue SO that the first gust of wind
sends it whirling earthward.
Some trees, such as the oaks and
beeches, retain great many of their
leaves all Winter, and only discard
them entirely in Spring. The sepa-
ration layer seems to be mature in
late Fall, but it may well be that
the layer is not quite thick enough
and needs the added soaking and de-
cay of Winter to complete the process,
so that March winds and April rains
may carry away the last of the
withered leaves.
although it is sometimes said that
the extra urge of new buds is need
ed to push the old leaves off, a close
inspection will indicate that the rela-
tive position of the buds to the old
leaves does not bear out this idea.
People of the Northern States often
envy the Southerner, thinking that
the latter must be lucky in not hav-
Ing to rake leaves from his lawn so
continuously in Autumn, but this is
I'd ne ne ledN6S Idll every year
in the South as they do in the North,
choosing the dry season. If the tree
held it's leaves during the season of
drought, the moisture loss would be
more than it could endure.
''The reds and colds and purples of
Autumn leaves are not brought about
by Jack Frost, as is commonly sup
posed, although frost sometimes does
kill the leaf so that it will fall be-
fore it's time, thus depriving the tree
of nourishment and weakening it.
Autumn coloring itself is entirely in
dependent of the action of frost and
may occur even in Midsummer. AS
the nourishment of the leaf is with
drawn into the tree, various pigments
and other products Of decomposition,
which have until now been hidden by
the green chlorophyll, show them
selves. Iron and minerals which the
sap has collected from the soil help
contribute to the pageant of Autumn
colors.
why are some Autumns more glo-
rious than others and why is the COL
oring less brilliant on our Pacific
Coast than in eastern Canada and
the Northeastern States Why are
our native trees more subdued in hue
when grown in the more humid cli-
mate of Europe? Moisture is the
color gauge. A long, dry Autumn
produces the finest color carnival, and
IopO Iru Autumn G penerallu oh r..