400 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
case of such plants as Vernonia fasWkulata. in particular, whose 
home here is on the prairie, and which produces a large crop of 
easily distributed seed, the only reason for it not being found at 
Station II just as at Stations I, III and IV, is chance seed dis- 
persal, as it is well able to endure the conditions. Because of the 
accidents of chance seed dispersal in so narrow a strip as the 
tract under consideration many plants that are native to the 
scattered groves of this region are missed. 
Of the plants found at Station II, the lower part of the bluff 
face, 14 per cent are not found elsewhere. The total flora of this 
station is the smallest of all, being only forty-three species, or 
twenty-six per cent of the total number as compared with sixty- 
five species or forty per cent for Station I, seventy-five species, or 
forty-six per cent, for Station III, and fifty-six s'peoies, or thirty- 
four per cent, for Station IV. Of the plants not found elsewhere 
1 tubus idaeus var. acideatissirniis would be expected at least in 
Stations I and III, but for the chance work of birds in distribut- 
ing seed, Verbena angustijolia is certainly a stray and should 
appear higher upon the hill, or on the sandy bottom, Phleum 
pratense, which is probably introduced, must be classed as a stray 
that could flourish at any station, though poorly at Station IV. 
Gymnocladus dioica appears to belong properly in the rich woods 
of Station II, near the foot of the bluff, where protection is good, 
both from drouth and from flood. Aster muliifloris var. exiguus, 
found only at this station, is perhaps a stray, for it frequents the 
sandbanks on the flat and the hills elsewhere. Of the plants 
found at Station II, thirty-seven per cent occur at Station I. 
sixty-five per cent of them at Station II, and sixteen per cent of 
them at Station IV. 
Station III has thirty-seven per cent of species not found 
elsewhere. It has the greatest total number of species of all the 
stations, namely, seventy-five per cent, due to its being located 
between the high prairie and the lower bluff woodland. It has 
eighteen species found also at Station IV, and twenty-eight 
species found also at Station II. Singularly, it has twenty species 
found on the river flat at Station I. Typical of the hardy plants 
that extend down to it from Station IV we have Solidago rigida, 
Rosa pratincola, Monarda mollis , Aster ptarmicoides, and Am- 
brosia .p silo st achy a. These, while at home on the dry prairie, are 
able to extend their range down the wooded bluff face as far as 
