Evening star., 1932-10-23
PLANTS PRODUCING
ROCKS DISCOVERED
Rapid Waters of Tributary of
Potomac Yield New Mi
mute Species.
BY THOMAS r. HENRY.

A new race of infinite5imaly minute
plants that build rocks has been found
by geologists of the Geological Survey
in the rapid waters of Furnace Greek,
little mountain stream that flows
into the Potomac at Harpsrs Ferry.
Discovery of this plant. ranging from
one 100, ,C00th to cnc 200, ,000th of an
inch in length, may provide an impor-
tart clue to the earliest days Of life on
earth. 1t is the smallest known spe-
cies of those microscopic plants, the
blue green algae. which literally were
building up mountains nearly a billion
years ago and which are believed to have
been among the earliest living thing;
They still are carrying on their ancient
job at Harpers Ferry, although en- a
reduced scale.
Found Among Pebbles.
This remarkable little pant was
, found BY David White and Charles B.
Read of the survey staff and Marshall
A Howe of the New York Botanical
Garden, and has Just been described
scientifically by DR.. Howe. Its dis
covery resulted from examination of
curious pebbles from the stream bed
which did not appear to be the product
OF any of the better known algae in the
Harpers Ferry waters. A popularity OF
this organism is that it appears to
build up one kind Of pebble in the
rapidly flowing parts of the stream and
a strikingly different kind in the quiet
pools where abundant sunlight has a
chance to penetrate.
The way this plant makes stones is
explained in the Geological Survey an
nouncement of the discovery. Like most
plants, this minute living thing pos
sesses the property Of photosynthesis, BY
| which carbohydrates are built up from
carbon dioXide and water through the
action of chlorophyll-the extremely
complicated compound responsible for
| the green color of leaves-in the pres
| ence of sunlight. Life on earth depends
| largely on this process.
! Calcium is held in solution in water
| The photosynthesis carried on by the
algae in some way changes the chemical
composition of the water so that 1t
cannot hold as much calcium. This is
deposited about the algae as limestone
! crust. Iron and manganese, also held
in solution in the water, are liberated
by the photosynthesis process. but ap-
parently in varying degrees depending
on light conditions.
! Darker Pebbles in Rapids.
| In the rapids, especially in the shaded
recesses, the superficial crust of the
pebbles tends to be black or rust colored
In the quieter water it is olive brown
or ash colored Chemical analysis shows
/ that iron and manganese are much
more abundant in the darker crusts
while the lighter are composed mostly
| of calcium
| From the more rapidly flowing water
of the stream were obtained rocklike
| deposits of lime of the kind known to
| geologists as 'trayertine," apparently
| largely due to the same organisms
| Cross sections of this rock show lam
mated structure. with the darker
| layers, indicating an abundance Of iron
occurring at irregular intervals and ir
irregular sizes. This popularity may
afford another natural calendar which
further study might enable geologists
to apply in studying conditions of the
distant past.
1t is suggested in the Geological Sur.
vey report Of the find that iron-caus
ing the darker layers-is deposited mos
abundsntly in dry seasons when tn,
water in which the algae are at worl
is low. Thus the iron and marganes,
deposit for the year 1880, when one o
the greatest droughts in history oc
CURED, was especially notable.