100 
Mr. Knight on the Direction oj 
observable during the conversion of a seed into a plant arc 
amongst the most interesting that occur in vegetation, I 
commenced the experiments, an account of which I have now 
the honour to request you to lay before the Royal Society. 
I conceived that if gravitation were the cause of the descent 
of the radicle, and of 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 motion and conse- 
quent distribution of the true sap afforded by the cotyledons : 
and as gravitation could produce these effects only whilst the 
seed remained at rest, and in the same position relative to 
the attraction of the earth, I imagined that its operation would 
become suspended by constant and rapid change of the posi- 
tion 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 another 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 their 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 as tangents to its curve, 
some pointing backwards, and others forwards, relative to its 
motion ; and others pointing in opposite directions in lines 
parallel with the axis of the wheels. The whole was inclosed 
in a box, and secured by a lock, and a wire grate was placed 
