same agent, by operating on bodies so differently 
organized as the radicle and germen of plants 
are, may occasion the one to descend and the 
other to ascend. I conceived that if gravitation 
were the cause of the descent of the radicle, and 
the ascent of the germen, it must act either by 
its immediate influence on the vegetable fibres 
and vessels during their formation, or on the mo- 
tion and consequent distribution of the true sap 
afforded by the cotyledons; and as gravitation 
could produce these effects only while the seed 
remained at rest, and in the same position re- 
lative to the attraction of the earth, I imagined 
that its operation would become suspended by 
constant and rapid change of the position of the 
germinating seed, and that it might be counter- 
acted by the agency of centrifugal force. Having 
a strong rill of water passing through my garden, 
I constructed a small wheel similar to those 
used for grinding corn, adapting a wheel of a 
different construction, and formed of very slender 
pieces of wood, to the same axis. Round the 
circumference of the latter, which was eleven 
inches in diameter, numerous seeds of the garden 
bean, which had been soaked in water to produce 
the greatest degree of expansion, were bound at 
short distances from each other. The radicles of 
these seeds were made to point in every direction, 
some towards the centre of the wheel, and others 
in the opposite direction, others at tangents to 
its curve, some pointing backwards and others 
forwards relative to its motion, and others point- 
ing in opposite directions in lines parallel with 
the axis of the wheels. The whole was enclosed 
in a box and secured by a lock, and a wire-grate 
was placed to prevent the ingress of any body 
capable of impeding the motion of the wheels. 
The water being then admitted, the wheels per- 
formed something more than 150 revolutions ina 
minute, and the position of the seeds relatively to 
the earth was as often perfectly inverted within 
the same period of time, by which I conceive 
that the influence of gravitation must have been 
wholly suspended. In a few days the seeds began 
to germinate ; I soon perceived that the radicles, 
in whatever direction they were protruded from 
the position of the seed, turned their points out- 
wards from the circumference of the wheel, 
and in their subsequent growth receded nearly 
at right angles from its axis. The germens, on 
the contrary, took the opposite direction, and in 
a few days their points all met in the centre of 
the wheel. Three of these plants were suffered 
to remain on the wheel, and were secured to its 
spokes to prevent their being shaken off by its 
motion. The stems of these plants soon extended 
beyond the centre; but the same cause which 
first occasioned them to approach its axis still 
operating, their points returned and met again 
at its centre. The motion of the wheel being in 
this experiment vertical, the radicle and germen 
of every seed occupied during a minute portion 
of time in each revolution precisely the same po- 
VEGETABLE PHYSIOLOGY. 
sition they would have assumed had the plants 
vegetated at rest; and as gravitation and centri- 
fugal force also acted in lines parallel with the 
vertical motion and surface of the wheel, I con- 
ceived that some slight objections might be urged 
against the conclusions I felt inclined to draw. 
I therefore added to the machinery I have de- 
scribed another wheel, which moved horizontally 
over the vertical wheels; and to this, by means 
of multiplying wheels of different powers, I was 
enabled to give many different degrees of velo- 
city. Round the circumference of the horizontal 
wheel, whose diameter was also eleven inches, 
seeds of the bean were bound as in the experi- 
ment which I have already described, and it was 
then made to perform 250 revolutions in a mi- 
nute. By the rapid motion of the water-wheel, 
much water was thrown upwards on the hori- 
zontal wheel, part of which supplied the seeds 
upon it with moisture, and the remainder was 
dispersed in a light and constant shower over 
the seeds in the vertical wheel, and on others 
placed to vegetate at rest in different parts of 
the box. Every seed on the horizontal wheel, 
though moving with great rapidity, necessarily 
retained the same position relative to the at- 
traction of the earth, and therefore the opera- ’ 
tion of gravity could not be suspended, though 
it might be counteracted in a very considerable 
degree by centrifugal force; and the difference 
I had anticipated between the effects of rapid 
vertical and horizontal motion soon became 
sufficiently obvious. The radicles pointed down- 
wards about ten degrees below, and the germens 
as many degrees above, the horizontal line of the 
wheel’s motion, centrifugal force having made 
both to deviate eighty degrees from the perpen- 
dicular direction each would have taken had 
they vegetated at rest. Gradually diminishing 
the rapidity of the horizontal wheel, the radicles 
descended more perpendicularly, and the germens 
grew more upright, and, when it did not perform 
more than eighty revolutions in a minute, the 
radicle pointed about forty-five degrees below, 
and the germen as much above, the horizontal 
line ; the one always receding from, and the other 
approaching to, the axis of the wheel. I would 
not, however, be understood to assert that the 
velocity of 250 or 80 horizontal revolutions in a 
minute will always give accurately the degrees 
of depression. and elevation of the radicle and 
germen which I have mentioned ; for the rapidity 
of the motion of my wheels was somewhat di- 
minished by the collection of fibres of confervee 
against the wire grate, which obstructed in some 
degree the passage of the water; and the ma- 
chinery having been the workmanship of myself 
and my gardener, cannot be supposed to have 
moved with all the regularity it might have done 
had it been the work of a professed mechanic. 
But I conceive myself to have fully proved that 
the radicles of germinating seeds are made to 
descend, and their germens to ascend, by some 
