400 ON THE SUPPOSED BOTANICAL PROOFS OF THE 



does not account for the facts we may as well abandon all attempts 

 at understanding- the useful arrangements in organisms. 



Sachs has used the term anuotropism to express the fact that 

 the various organs of a plant assume the most diverse directions of 

 growth under the influence of the same forces. He also states that 

 anisotropism is one of the most general characteristics of vegetable 

 organization, and that it is quite impossible to form any idea as to 

 how plants would appear or how they could live if their different 

 organs were not anisotropic. Since anisotropism is nothing more 

 than the expression of different kinds of susceptibility to the action, 

 of gravity, light, &c., it is obvious that the configuration of the 

 plant is to be traced to siich specific susceptibilities. 



Now these specific susceptibilities cannot have been produced by 

 the direct effect of the various external influences (as was shown 

 above), and the only other possible explanation is to recognise them 

 as adaptations, and to admit that they have arisen by the opera- 

 tion of natural selection upon the general variability of plant 

 organization. 



Simple as these conclusious are, I have failed to meet with them 

 in any of the writings of botanists, and they may perhaps be of use 

 in helping to shake the vaguely-felt opinion that the characters of 

 plants are to be chiefly referred to the direct action of external 

 influences. 



At all events it cannot be maintained that the phenomena of 

 anisotropism support the opinion mentioned above ; and the mere 

 assertion that it is highly probable that hereditary characters 

 arise as the result of external influences, is no more than the ex- 

 pression of an unfounded individual opinion. It is remarkable that 

 Detmer should make such an assertion as the outcome of his dis- 

 cussion of the reversed T/wja-shoot, &c., for even if we admit that 

 the dorso-ventral structure of the shoot is as Detmer believes 

 the direct and primary effect of the action of light, the experiment 

 with the reversed shoot would prove that no part of this effect 

 has become hereditary. Although the upper side of the shoot 

 has produced the palisade parenchyma under the influence of light. 

 for thousands of generations, there is nevertheless no tendency 

 towards the establishment of any hereditary effect, for as soon us 

 the upper side of the growing shoot is artificially transformed into 

 the under side, its normal structure is at once abandoned. Hence 



