Montgomery County sentinel. [volume] (Rockville, Md.) 1855-1974, 1855-12-08
LIGHT AND SHADE.

LIGHT AND SHADE.
Light produced by the rays of the sun
is a most important agent in the devel-
opement of plants, the green color of
their leaves, fruits, twigs, &C., being
generated by its action; but it is not ne
cessary to have the direct solar beam
dilfused daylight is sufficient, although
the action is not, in this case, so rapid
and energetic as when aided by the
bright rays of the sun. Mould and some
kinds Of mushrooms, however, grow and
thrive without light. LISA well known
fact, that most of the mushrooms used in
Paris are grown in the catacombs under
that city, where the light of the sun is
never seen; but trees and the plants usu-
ally cultivated cannot long exist in a
healthy state without its presence.
All green and living plants exposed to
the light, and living upon atmospheric
air, obtain most of their carbon from its
carbonic acid (Which they imbibe and
decompose,) their hydrogen from its
moisture, and their nitrogen partly from
the ammoniacal vapor which therein ex-
lists. But in the absence Of light, oxygn
is withdrawn from the air, the carbonic
acid emitted, and plants in the dark de-
teriorate, the air in which they are con-
fined; whereas, when exposed under the
open canopy of heaven to the alterna-
tions of light and darkness, sunshine and
gloom, exactly the reverse is the case
Hence we have the fullest reason to be-
lieve that plants are hoarished by the
carbonic acid of the atmosphere, which is
absorbed directly by their leaves from
the surrounding air, and also by their
roots, when dissolved in ran-water; and
further, that the rapidity of the decom-
position bears direct relation to the in
tensity of the light
In the tropics, for instance, vegetation
is wonderfully active, and this is due as
much to the brighter sunshine as to the
more elevated temperature of these parts
There is no difficulty in obtaining in ;
stove, nor in conservatory, an atmos
phere as warm, and, il necessary, ~
moist as may be desired, and the plant
of hot countries may be cultivated Wit
certain degree of success in such SIT
uation; but they never exhibit the thirty
ing and beautiful appearance, the deep
green color characteristic of health, be
longing to them in their natural state
We may substitute artificial warmth TO
that of the sun, but we cannot suppl,
the place of its light.
How necessary light is to the healtl
Of plants may be inferred from the ca
gerness with which they appear to lonl
for it. How intensely does the sunfiowe
watch the daily course Of the sun J Hoy
do the countless blossoms nightly drool
; when he retires, and the blanched plan
! strive to reach an open chink through
which his light may reach it Thus
potato has been observed to grow up il
quest of light from the bottom Of wei
; twelve feet deep; and in dark cellar
shoot of twenty feet in length has bcel
met with, the extremity of which ha'
reached and rested at an open window
That the warmth of the sun has com
paratively little to do with this specili
u action of his rays on the chemical func
tions of the leaf is illustrated by some in
: teresting experiments Of Mr.. X. Hunt
, of England, on the effect Of rays of ligh
: of different colors on the growing plant
! He sowed cress seed, and exposed differ
ont portions of the soil in which the seed
were terminating to the action Of the red
yellow, green and blue rays, which wer
: transmitted by equal thicknesses of so
! lntions of these several colors. "Afte
q ten days, there was under the blue fui
: crop Of crcss Of as bright green as an
! which grew in full light, and far NOR
abundant The crop was scanty undo
: the green fluid, and Of a pale-yellow, IN
: healthy color Under the yellow solu
G ton, only two Or three plants appeared
b but less pale than those under the greer
/ while beneath the red few more plant
i came up than under the yellow, thong
y they were also of an unhealthy color
G The red and blue bottles being now mu
tually transferred, the crop formerly be
G meath the blue in a few days appeare
r blighted while on the patch preyiousl
1 exposed to the rcd, some additions
plants sprung up" From the result
0 these experiments, it has been recon
q mended that a cheap blue glass be EN-
z ploycd for glazing lighthouses, conserve
tories, &C., instead Of the kind in com
G mon use.
/ Besides the rays of heat and Of light
{ the sunbeam contains what have bee
I called Chemical rays" not distinguish
4 able by our senses, but capable Of bein
@ recognized by the chemical effects the
f produce. These rays appear to differ !
e kind, as the rays Of different-colorc
light. 1t is to the action Of these chemi
cal rays on the leaf, and especially
3 those which are associated with the blu
: light in their collar beam, that the chen
= zeal influence Of the sun on the function
/ Of the leaf is principally to be ascribeC
4 On the contrary, there are importar
relations in respect TO Maoe, which NJ
: cessariIy have influence upon the powc
D Of promoting vegetation. Every farmC
: knows, that when soil has been shade
c for considerable time bya dense crop'
a clover, ray-grass, hemp, turnips, cal
bages, peas, &C., or is covered by buils
/, ings, boards, stones, shayings, saw dus
1 tan bark, chat, straw, coarse hay,