TT? MISSOURI BOTANICAL GARDEN. 
the case in the deep sloughs of the Varner and St. Francis 
rivers near Kennett, though at low water the knees emerge 
about two feet. But here and there dead knees, quite 
unconnected with standing trunks, or clearly belonging to 
the shells of old trees none of which are now living, rise 
some three feet beyond the level marked by the knees of 
existing trees. These vestiges of an earlier forest growth 
appear to indicate that when they were in their prime the 
water level stood several feet above the present flood 
level, and so far as can be estimated from the trees this 
was somewhere from two hundred to five hundred years 
ago. 
Professor R. Ellsworth Cail, who has made a geological 
study of the region in which these plants now appear to 
find their northernmost home, writes me that the Mis- 
sissippi river formerly without question flowed far to the 
west of its course to-day, and in comparatively recent 
geologic times cut away the opposing ridge below Cape 
Girardeau, and excavated its present channel and the low- 
lands around. Meantime it has swung across the valley 
several times, but its westward movement has been succegs- 
fully resisted by the remains of the great Tertiary plateau 
or northward deposit of the ancient Gulf, which extends 
from Florida to Mexico and northwards to this region, of 
which Crowley’s Ridge is believed to be the last remaining 
vestige in the middle valley. He mentions as interesting 
in connection with these changes in the Mississippi and its 
immediate valley, the fact that the Ohio long preserved its 
integrity to a point not far from the present site of 
Helena. He also states that there can be no question that 
these changes at times have been retarded by depression of 
the whole area, and at times hastened by elevation; that 
there have been comparatively recent times when all the 
region about northeast Arkansas and southeast Missouri 
was a veritable marshy waste; and that this condition has 
been several times repeated, with a synchronous ameliora- 
8 
