cijAr. V Movements of Plants 77 



loose soil, and have little straight radicles, be carefully 

 removed, and suspended in the air under a damp bell-jar 

 with the radicles pointing upwards or horizontally, in the 

 course of a few hours the radicles will all have turned 

 downwards. 



In the same way the growing shoots of plants may be 

 placed or artificially forced to grow in a horizontal position, 

 but if the shoot be strong enough and be not, for instance, 

 naturally a creeper, its character asserts itself as soon as it 

 is free from restraint, and the stem grows upwards. 



As long ago as 1806 Knight tried the effect of growing 

 young plants on a rotating wheel. When an apparatus of 

 this sort is devised, with seedlings suitably fixed on a 

 rotating disc, the young roots always grow outwards and 

 the young stems inwards. When the plane of rotation is 

 vertical the direct influence of gravitation is counteracted, 

 its direction being continually altered ; but in relation to the 

 so-called "centrifugal force" the roots and the stems grow 

 in consistently antagonistic directions, the stems against, 

 the roots in the direction of the acting force. 



There is a more modern apparatus called a klinostat, a 

 clockwork arrangement by which germinating seeds are 

 slowly rotated in a vertical plane, and as the relation of 

 the parts to the earth's axis is constantly changing, the 

 direct action of gravity is counteracted ; the result being, as 

 we would expect, that the young roots and stems grow in 

 totally indefinite fashion. 



No one will suppose that in normal conditions the roots 

 simply sink downwards passively, for they will force their 

 way into quicksilver, and besides the stem is influenced in 

 an exactly opposite way. It is certain that the parts of 

 plants are influenced by gravity, but not passively ; they 

 are living organs. 



It seems Hkely that the roots and the stems, ditfering as 



