Evening star., 1937-01-09
STARS, MEN AND ATOMS
Notebook of Science Progress i'm Field.
Laboratory and Study.
Laboratory and Study.
BY THOMAS R. HENRY.

When the great ice sheets crept down
from the Arctic over the northern part
Of the United States in the last glacial
period they buried forests and prairies
in their path. Life. plant and animal,
retreated slowly before them, but much
probably was wiped out.
But when the ice sheet secured the
land as far south as ST. Louis it left an
area 100 miles wide in Southwestern
Wisconsin which remained as an island
Of vegetation in the vast glacial waste.
according to report to the National
Academy of Sciences here from DR.. Nor
man G. FaSSett Of the University of Wis
conSin. Here some of the vegetation Of
the Middle West survived which else
where was destroyed. 1t persists to this
day and gives some idea of the kind of
plant life on the continent before the
ice sheets came.
Since the glacial period, Prof. FasSett
finds, these plants have had little power
of spreading and. except for a few
species, are confined to the island"
Some of them have close relatives out
side the region covered by the ice. They
are found mingled with plants from the
South which moved northward in the
wake of the retreating glaciers to repop-
ulate the drifted area.
One of the surviving plants Of the area
Is the miners lettuce, which is found
from New Mexico to California, and
northward as far as Alaska. The jeweled
shooting star, a slenderer plant than the
common shooting star of the prairies,
and with more brilliant flowers. also sur
vived. This flower also has been found
in Eastern Pennsylvania, south Of the
glacial margin, and a similar or closely
related plant is found in the Ozarks. A
peculiar species of aconite which grows
in the CatskillS has close relative in
this Wisconsin driftleSs area. kind OF
saxifrage, which grows south OF the
glaciated regions in Ohio. Indiana and
Missouri, is also found in the region.
Presumably this plant occupied con-
tinuouS Area before the glaciers ex-
terminated it\through most of its range.
Another plant range that was cut in
two by the ice drift was that of variety
of purSlane which survived in the
mountains from Pennsylvania to Georgia.
A distinct but very similar plant IS
found in the island" One plant which
migrated from the driftleSS area Is a
kind of shrubby st. Johns wort, which
appears to have fiourished around the
shores of glacial Lake Wisconsin, which
disappeared thousands of years ago.
From the present distribution Of the
plant it must have migrated to what is
now Lake Michigan, following the shores
of the lakes along the margin of the
melting glacier.
There were at least five advances of
the Wisconsin glaciation, separated by
ice-free interglacial periods, when plants
could spread. The present occurrence OF
very rare species Of lespedeza indi-
Gates that it spread after the fourth Wis
consin glaciation, but later was elm
mated from part of its regained terri
tory by the fifth glacier, for it grows
today in the driftlesS area and on land
covered by the third and fourth glacia-
tions.
The progressive cooling of the climate
as the great ice sheets moved down from
the north was recorded in tree rings OF
the period, according to another report