Febeuaey 3, 1911] 



SCIENCE 



177 



De Vries''^ is distinctly not prepared to 

 admit that mutations are described by the 

 theorem of Le Chatelier. 



The origin of new species, which is in part the 

 effect of mutability, is, however, due mainly to 

 natural selection. Mutability provides the new 

 characters and new elementary species. Natural 

 selection, on the other hand, decides what is to 

 live and what to die. Mutability seems to be free, 

 and not restricted to previously determined lines. 

 Selection, however, may take place along the 

 same main lines in the course of long geological 

 epochs, thus directing the development of large 

 branches of the animal and vegetable kingdom. 

 In natural selection it is evident that nutrition 

 and environment are the main factors. But it is 

 probable that, while nutrition may be one of the 

 main causes of mutability, environment may play 

 the chief part in the decisions ascribed to natural 

 selection. Relations to neighboring plants and to 

 injurious or useful animals, have been considered 

 the most important determining factors ever since 

 the time when Darwin pointed out their prevail- 

 ing influence. 



There is nothing very definite to be ob- 

 tained from Klebs."* 



The dependence of variable internal on variable 

 external condition gives us the key with which 

 research may open the door. In the lower plants 

 this dependence is at once apparent, each cell is 

 directly subject to external influences. In the 

 higher plants with their different organs, these 

 influences were transmitted to cells in course of 

 development along exceedingly complex lines. In 

 the case of the growing point of a bud, which is 

 capable of producing a complete plant, direct in- 

 fluences play a much less important part than 

 those exerted through other organs, particularly 

 through the roots and leaves, which are essential 

 in nutrition. These correlations, as we may call 

 them, are of the greatest importance as aids to 

 an understanding of form-production. When a 

 bud is produced on a particular part of a plant, 

 it undergoes internal modifications induced by 

 the influence of other organs, the activity of 

 which is governed by the environment, and as the 

 result of this it develops along a certain direc- 

 tion; it may, for example, become a flower. The 

 particular direction of development is determined 



""Darwin and Modern Science," 77, 1909. 

 "^ " Darwin and Modern Science," 228, 235, 242, 

 1909. 



before the rudiment is differentiated and is ex- 

 erted so strongly that further development ensues 

 without interruption, even though the external 

 conditions vary considerably and exert a posi- 

 tively inimical influence: this produces the im- 

 pression that development proceeds entirely inde- 

 pendently of the outer world. The wide-spread 

 belief that such independence exists is very pre- 

 mature and at all events unproven. 



The state of the young rudiment is the out- 

 come of previous influences of the external world 

 communicated through other organs. Experi- 

 ments show that in certain cases, if the efficiency 

 of roots and leaves as organs concerned with 

 nutrition is interfered with, the production of 

 flowers is affected, and their characters, which 

 are normally very constant, undergo far-reaching 

 modifications. To find the right moment at 

 which to make the necessary alteration in the 

 environment is indeed difficult and in many cases 

 not yet possible. This is especially the case with 

 fertilized eggs, which in a higher degree than 

 buds have acquired, through parental influences, 

 an apparently fixed internal organization, and 

 this seems to have predetermined their develop- 

 ment. It is, however, highly probable that it will 

 be possible, by influencing the parents, to alter 

 the internal organization, and to switch off devel- 

 opment on to other lines. 



Bailey is quite clear that the environ- 

 ment has a marked effect upon plants ; but 

 he is very far from formulating that effect, 

 as the following quotations will show :°° 



These differences [between individual plants] 

 arise as a result of every impinging force, soil, 

 weather, climate, food, training, conflict with fel- 

 lows, the strain and stress of wind and wave, and 

 insect visitors, as a complex resultant of many 

 antecedent external forces, the effects of crossing, 

 and also as the result of the accumulated force of 

 mere growth; they are indefinite, non-designed, 

 an expression of all the various influences to 

 which the passive vegetable organism is or has 

 been exposed; these differences which are most 

 unlike their fellows or their parents find the 

 places of least conflict and persist because they 

 thrive best, and thereby impress themselves best 

 upon their offspring. 



It is not too much to ask of climatology that 



it shall tell us why the northern climates develop 



saccharine elements and high colors, and why the 



«' Bailey, "The Survival of the Unlike," 32, 



309, 1896. 



