126 ON THE DIRECTION OF THE RADICLE 



described, and it was then made to perform 250 revolutions in a minute. 

 By the rapid motion of the water-wheel much water was thrown upwards 

 on the horizontal 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 vege- 

 tate 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 attraction of the 

 earth ; and therefore the operation of gravitation could not be suspended, 

 though it might be counteracted, in a very considerable degree, by con- 

 trifugal force : and the difference, I had anticipated, between the effects 

 of rapid vertical and horizontal motion soon became sufficiently obvious. 

 The radicles pointed downwards about ten degrees below, and the ger- 

 mens as many degrees above, the horizontal line of the wheel's motion ; 

 centrifugal force having made both to deviate 80 from the perpendicular 

 direction each would have taken, had it vegetated at rest. Gradually 

 diminishing the rapidity of the motion 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 45 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 of eighty 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 some- 

 times diminished by the collection of fibres of conferva against the wire 

 grate ; which obstructed 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 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 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 have observed) 

 is increased in length only by new parts successively added to its apex or 



