Saint Mary's beacon. [volume] (Leonard Town, Md.) 1867-1983, 1876-11-09
AUTUMN LEAVES.

What is the cause Of these beautiful
and endlessly diversified colorings OF
the leaves in autumn The immediate
cause is the lessened activity of their
pores, or breathing organs, owing to the
feebler Illuminating power of the sun,
which is nearer the horizon at mid
day, shines upon it more oblIquely, and
sets sooner. II has been observed that
plants bend from the red or calorific
rays of the suns spectrum, instead of
toward them, as they are found to do
in regard to every other ray. From
this curious circumstance the inference
has been drawn that the effect of these
rays is to check the vegitative process
ses, and favor the formation and growth
of the blossoms and fruit in which the
activity of every plant terminates
Light is only secondary cause Of ac-
hyity In blossoms, while it is the prin-
clpal cause OF activity in leaves. II
the deficiency of light is compensated
by an increase OF heat, blossoms NAV be
made active even in total darkness, W bile
the leaves will present only a very
imperfect vitality. Thus we see that
heat iavors the production of the bios
som, while it has little or no effect upon
the leaves. And IN accordance with
this, 1t has been further observed that
the heat rays are more powerful in au-
tumn than at any other season; while
the actinic rays which stimulate germi-
nation, and the luminous rays which
are required for the formation Of the
tissues and their products. are proper
tionatcly diminished. The rise Of the
sap in spring is quickened by the act-
ni>m which is then most abundant in
the solar beams; the secretion of car
bon in summer is due to the greater
, predominsnce of light: and the rever-
sion Of the sap, the ripen:ng of the fruit,
and the discoloration of the leaf in au-
tumn, may be traced to the increased
power of the parathermic influence
from which the plant is found to bend,
and which appears TO be modified
form of heat. The distribution of plants
over the surface of the earth, as well
as their periodic changes, are depen-
dent upon these causes,-the greater or
less amount OF actinism, light or heat in
the climates, and the season in which
they grow. Given the proportion oi
, these different principles of the sun.
shine Of differentcountrics and seasons,
and it will be easy to predict the char.
acter Of their vegetation and the nature
of their vegetable products.
Bearing these curious influences in
mind, ii is easy to understand why. with
the diminished light of the shorter days
OF autumn, the natural stimulant of veg
citation should be correspondingly with.
drawn, and the circulation Of the SAP
through the lamina. or blade of the
leat, cease. Carbon cannot be formed
from the atmosphere except under the
influence Of light; and when this slim.
ulant is weakened, the vital powers ol
the leaves are proportionately dimin.
ished. and the affinity which the Y have 70,
oxygen acts with little opposition. The
great natural ife-process Of deoxida,ior
not only stops but is reversed Oxy.
gen is absorbed. and carbon The pro.
duct Of cumbustion, is given of; ant
the ehlorophyl. or that carboaaeeou.
product which gives The green healthy
color to leaves. Is slowly oxodixed. anS
rusts away into the various tints Of su
tumn. The hues of .he foliage become
brighter as the process Of oxida,ion goe.
On; those OF early autumn being dull
aud dark green, passing iafcr in Ii,