NATURAL HISTORY: 
with moisture, and the remainder 
was dispersed, in alight and constant 
shower, over the seeds in the verti- 
cal 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, there- 
fore the operation of gravitation 
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 
-Tapid, vertical, and horizonial mo- 
tion, soon became sufiiciently ob- 
vious. The radicles pointed down- 
wards about ten degrees below, and 
the germens as many degrees above, 
_the horizontal line of the wheels’ 
‘motion; centrifugal force having 
made both te deviate 80 degrees 
from the perpendicular direction 
each would have taken, had it vege~ 
tated at rest. Gradually diminish. 
_ ing the rapidity of the motion of the 
horizontal wheel, the radicles de- 
scended more perpendicularly, and 
the germens grew more upright; 
and when it did not perform more 
than 80 revolutions in a minute, the 
radicle pointed about 45 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 
wheelj 
_ I would not, however, be under- 
stood to assert that the velocity of 
250, or of 80 horizontal revolutions 
ina minute, will always give accu- 
“rately the degrees of depression and 
- elevation of the radicle and germen, 
which I have mentioned; for the 
fapidity of the motion of my wheels 
You. XLVIII. 
929 
was sometimes diminished by the 
collection of fibres of conferva 
against the wire grate; which ob- 
structed in some degree the passage 
of the water; and the machinery, 
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 made by a professional mecha- 
nic. But I conceive myself to have 
fully proved that the radicles of 
germinating seeds are made to de- 
scend, and their germens to ascend, 
by some external cause, and not by 
any power inherent in vegetable 
life: and I see little reason to doubt 
that gravitation is the principal, if 
not the only agent employed, in this 
case, by nature. I shall, therefore, 
endeavour to point out the means by 
which I conceive the same agent 
may produce effects so diametrically 
Opposite to each other. 
The radicle of a germinating seed 
(as many naturalists haye observed) 
is increased in length only by new 
parts successively added to its apex 
or point, and not at all by any ge- 
neral extension of parts alread 
formed ; and the new matter, which 
is thus successively added, unquese 
tionably descends in a fluid state 
from the cotyledons. On this fluid, 
and on the vegetable fibres and ves. - 
sels whilst soft and flexible, and 
whilst the matter which composes 
them is changing from a fluid to a 
solid state, gravitation, I conceive, 
would operate sufficiently to give an 
inclination downwards to the point 
of the radicle; and as the raudicle 
has been proved to be obedient to 
centrifugal force, it can scarcely be 
contended that its direction would 
remain uninfluenced, by gravitation. 
I have stated that the radicle is 
increased in length only by parts 
30 successively 
