Evening star., 1938-12-24
Of Sturs, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
BIZ Thomas r. Henri.

10 lie IN changing world Is being
| studied by botanists of the Carnegie IN
| stitution Of Washington.
The mechanisms by which plant
| must live are fore-ordained. 1t cannot
| change them. When it's surroundings
| change it must adjust itself so that its
| life machinery can function under the
new conditions The ingenuity" by
which the plant world accomplishes such
| adjustments furnished one of the ex-
| hibits arranged for trustees of the insti-
| tuition last week
Sometimes it can make the adjustment
| only by changing or restricting its habi-
| tat good example of this, say the
| Carnegie botaniStS, is the Pacific Coast
| redwood. Today it is confined to a mar
row belt along the Pacific Coast, extend
| ing from Southern Oregon to Central
| California. 1t was once widely distrib-
| uted over most of the Northern Hemi-
| sphere. Fossil cones, leaves and logs
found in tie rocks of many lands show
that in structure and composition the
redWoods that flOurished millions of
| years ago We're essentially the same as
| those which grow today And the proc
eSses by which it grows today are exactly
| the same as they were 10000 600 years
ago.
But other plants. instead of retreating
to habitat favorable to them, have con-
quered adverse environments Con-
fronted by change, a plant must either
( retreat, change its form SO that its life
processes can function, or become sex
unct If its home becomes desert it
must learn" by a series of those ey-
pelments which constitute evolution. to
live in the desert. In some ways, it is
pointed out, plants are more adaptable
and, IN sense, more progressive, than
animals They are more ruthless in
eliminating the unfit and preserving only
the fit until race is evolved capable of
coping with almost any specific condi-
uon, Hence there are few corners of
the world, however hostile, that are
completely devoid Of plant life.
The process whereby they make their
1000 and build up their bodies says
the Carnegie report, is essentially the
same IN all green plants, however diverse
tneE may appear to be and whether they
grow on land or in the sea. in the tropIcs
or IN the deserts. BY means of the Dhos-
| pAateS and carOonates Or calcium and
magnesium present in the leaves. The
plant aDsorbS carbon dloXiGe from the
air, and through its roots it obtains Wa
| ter from the soil. Under the influence
OF hight which is absorbed by the green
coIorlng matter of the plant the carbon
dloXloe and water are converted into
substances such as sugar and oxygen is
liberated into the air This process is
Known as photosynthesis. It does NOT
occur III the dark. In the absence of
lGht the plants consume the food they
have produced, absorbing oxygen from
and hbarating carbon dioxide into the
air.
II will be seen that the plant de-
pends on It's physical environment Tor
three elements essential to its growth
caroon dloXlde from the air, water from
the soil and light from the sun. The
availability of these elements varies
"lde!y III dl1terent parts of the earth
ana az Qlfterent times. In order to main
tain the life essential photosynthesis the
plant must change its form and life
habit if 1t is to make the best use of the
opportunities for securing these essen
tlal elements that its physical environ
ment presents.
CERTAIN plants have undergone spe-
CARNATIONS which make it possible Tor
them to live under the severe conditions
OF the desert. The most general change
IS reduction IN the size of the plant and
the area of its green surface. which les
sens the water requirement. but lessons
also Its capacity for phOtosynthesis and
growth, One of the commonest features
! OF specialization is the DEVELOPMENT of
Water-storing tissue in the stems. which
make the plant immune to long, rainless
periods
For example, the green -stemmed des-
ert tree Cercidium has very small leaves
in the rainy season. 1t depends on the
scanty water supply of deep, rocky soil
announcer has very small surface in
relation to its volume. It's roots are very
near the surface of the soil and function
Tor only few weeks Of the year when
the SOIL is wet. The specifications
1ound in these two common types of des-
eft plants are in strong contrast to the
normal tree of moist climates.
Striking variations occur within q
single plant species growing in nature
under varying climatic conditions. This
is Illustrated by the Western yarrow, It
lnhablts regions of markedly different
climatic conditions and is composed of
different races. The races which occur
in the area ranging from the mild, humid
coast of California up to the Alpine
Arctic crest of the Sierra Nevada and
down the Eastern flank to the arid Great
Basin show an impressive diversity of
form.
Gradual change in climatic condi-
tons is accompanied by a corresponding
change in the form and composition OF
the vegetation as a whole. On the
Great Plains three major communities
OF plants have replaced each other in
the past as the climate has shifted from
Wet-co9 to dry-hot phases, or the re-
verse. So also changes of land form,
soil, vegetation and human populations
have accompanied the recent period OF