54 WONDERS OF PLANT LIFE 



little to do with this strange tendency on the 

 part of plants. Years ago a president of the Royal 

 Horticultural Society, Mr. J. A. Knight, germin- 

 ated Bean seeds on the rim of a vertical wheel, 

 which was always kept revolving. Arrangements 

 were also made to keep the seeds in a moist con- 

 dition favourable to growth. It was found that 

 the roots of the seedlings now grew outwards 

 away from the centre of the wheel. From this it 

 would appear that when the action of gravitation 

 was overthrown by the centrifugal force of the 

 revolving wheel the little plants were influenced 

 by the new power. Thus it seems to be evident 

 that the influence of gravitation in directing the 

 course of the roots of seedlings is considerable. 

 This does not by any means offer a complete 

 solution of the problem ; for whilst the root 

 goes downwards the shoot with almost equal 

 precision directs its growth upwards. It must be 

 admitted that there is something more than a 

 mere mechanical influence at work. We are 

 indeed brought face to face with one of those 

 mysteries which are as inscrutable as life itself. 

 The most that can be said is that the radicle of 

 the seedling is endowed with a geotropic tendency 

 which impels it to bury itself in the earth, the 

 tendency of the shoot meanwhile being in an 



