SALT AND WATER IN LIFE AND GROWTH 147 



the formation of the stripes. This important fact is defi- 

 nitely proved by Liesegang's discovery of periodic stripe 

 formation. 



We have so far assumed that the development of the 

 artificial structures described is due to the expanding in- 

 fluence of the osmotic pressure. Some scientists have pro- 

 pounded an opposing view to the effect that gravity should 

 be considered the important factor. This would mean that 

 the development of these structures depends upon their 

 floating in the solution in which they form. But such a 

 view is strikingly contradicted by experiments. Certain 

 artificial structures will grow in all directions without regard 

 to the action of gravity (Fig. 56). The same fact is proved 

 by the observation that a counteracting osmotic pressure 

 can suppress the growth (Fig. 57). 



10. MOVEMENTS OF NATURAL AND ARTIFICIAL PLANTS. 

 ARTIFICIAL STRUCTURES GROWING OUTSIDE SOLUTIONS 



Even more striking are the movements of these artificial 

 plants and their similarity to the slow movements of real 

 plants. As is well known, most plants, particularly their 

 flowers, grow towards the light. Light is the real life force 

 of plants; it is indispensable for the converting of the gas- 

 eous carbon dioxide of the air into the solid material of the 

 plant body. Does a plant possess some sort of intelligence, 

 as it seeks the light by growing towards it? 



This idea seems to be disproved by the fact that some 

 artificial structures also grow to the light, even though they 

 do not need it at all for building up their bodies. No one 

 would ascribe to these structures anything like an intelli- 

 gence or an instinct. Simple physical conditions are rec- 

 ognized as the cause of the bending toward the light. The 

 enveloping membrane of their stems is rendered somewhat 

 softer and more flexible where it is hit by the light rays. It 



