246 Influence of Environment on Planis 
Good manuring is in the highest degree favourable to vegetative 
growth, but is in no way equally favourable to the formation of 
flowers. The constantly repeated expression, good or favourable 
nourishment, is not only vague but misleading, because circum- 
stances favourable to growth differ from those which promote repro- 
duction; for the production of every form there are certain favourable 
conditions of nourishment, which may be defined for each species. 
Experience shows that, within definite and often very wide limits, it 
does not depend upon the absolute amount of the various food sub- 
stances, but upon their respective degrees of concentration. As we 
have already stated, the production of flowers follows a relative 
increase in the amount of carbohydrates formed in the presence of 
light, as compared with the inorganic salts on which the formation of 
albuminous substances depends!. The various modifications of flowers 
are due to the fact that a relatively too strong solution of salts is 
supplied to the rudiments of these organs. As a general rule every 
plant form depends upon a certain relation between the different 
chemical substances in the cells and is modified by an alteration of 
that relation. 
During long cultivation under conditions which vary in very 
different degrees, such as moisture, the amount of salts, light in- 
tensity, temperature, oxygen, it is possible that sudden and special 
disturbances in the relations of the cell substances have a directive 
influence on the inner organisation of the sexual cells, so that not 
only inconstant but also constant varieties will be formed. 
Definite proof in support of this view has not yet been furnished, 
and we must admit that the question as to the cause of heredity 
remains, fundamentally, as far from solution as it was in Darwin’s 
time. As the result of the work of many investigators, particularly 
de Vries, the problem is constantly becoming clearer and more 
definite. The penetration into this most difficult and therefore 
most interesting problem of life and the creation by experiment 
of new races or elementary species are no longer beyond the region 
of possibility. 
1 Klebs, Kiinstliche Metamorphosen, p. 117. 
